Climate and average weather in Jōetsu
In Jōetsu, the summers are muggy, hot, showery, and partly cloudy and the winters are cold, snowy, and mostly cloudy.
Over the course of the year, the temperature in Jōetsu typically varies from 1°C to 30°C, and is rarely below -2°C or above 34°C. August is the hottest month of the year, while January is the coldest.
Based on the travel score, the best times of year to visit Jōetsu for warm-weather activities are from late April to mid July and early September to late October.
- Hottest
- Aug
- 30°
- Coldest
- Jan
- 1°
- Wettest
- Jan
- 253 mm
- Driest
- May
- 92 mm
- Rain / yr
- 1946 mm
- 202 wet days
- Daylight
- 9.4–14.6 h
- shortest–longest
- Elevation
- 10 m
- 37.1°N
- Clearest
- Apr
- 59% cloud
Jōetsu is city in Niigata Prefecture, Japan.
- Density
- 195/km²
- people per km²
- Founded
- 1971
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Jōetsu weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around late April to mid July.
Temperature through the year
Daily average highs and lows in Jōetsu, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 3.4 months, from June 15 to September 24, with daily high temperatures above 24°C. The hottest month of the year in Jōetsu is August, with an average high of 30°C and low of 24°C.
The cool season lasts 3.5 months, from December 6 to March 20, with daily high temperatures below 10°C. The coldest month of the year in Jōetsu is January, with an average low of 1°C and high of 6°C.
Days typically run about 6°C warmer than nights, with the widest day–night swing (around 7°C) in April.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 6 | 6 | 10 | 15 | 20 | 24 | 28 | 30 | 26 | 20 | 14 | 9 |
| Avg low (°C) | 1 | 1 | 3 | 8 | 13 | 18 | 22 | 24 | 20 | 14 | 8 | 4 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 6 | 1 |
| Feb | 6 | 1 |
| Mar | 10 | 3 |
| Apr | 15 | 8 |
| May | 20 | 13 |
| Jun | 24 | 18 |
| Jul | 28 | 22 |
| Aug | 30 | 24 |
| Sep | 26 | 20 |
| Oct | 20 | 14 |
| Nov | 14 | 8 |
| Dec | 9 | 4 |
How hot and cold Jōetsu really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the hottest afternoons, once humidity is folded in, Jōetsu feels like about 34°C (around August 6). About 30 days a year carry some heat stress, peaking in August.
On the coldest nights, wind chill pulls the feels-like down to about -4°C (around January 30), with roughly 93 freezing days a year (feels-like at or below 0°C), worst in January.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°C) | 6 | 6 | 9 | 15 | 20 | 24 | 30 | 33 | 26 | 20 | 14 | 9 |
| Air high (°C) | 6 | 6 | 10 | 15 | 20 | 24 | 28 | 30 | 26 | 20 | 14 | 9 |
| Feels-like low (°C) | -3 | -3 | 0 | 6 | 13 | 18 | 22 | 24 | 20 | 14 | 7 | 0 |
| Air low (°C) | 1 | 1 | 3 | 8 | 13 | 18 | 22 | 24 | 20 | 14 | 8 | 4 |
| Feels-like high (°C) | Air high (°C) | Feels-like low (°C) | Air low (°C) | |
|---|---|---|---|---|
| Jan | 6 | 6 | -3 | 1 |
| Feb | 6 | 6 | -3 | 1 |
| Mar | 9 | 10 | 0 | 3 |
| Apr | 15 | 15 | 6 | 8 |
| May | 20 | 20 | 13 | 13 |
| Jun | 24 | 24 | 18 | 18 |
| Jul | 30 | 28 | 22 | 22 |
| Aug | 33 | 30 | 24 | 24 |
| Sep | 26 | 26 | 20 | 20 |
| Oct | 20 | 20 | 14 | 14 |
| Nov | 14 | 14 | 7 | 8 |
| Dec | 9 | 9 | 0 | 4 |
Average hourly temperature in Jōetsu
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on August afternoons, near 30°C, and coldest before dawn in January, near 1°C.
Jōetsu weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 6° / 1° | 253 | 25.9 | 16.3 | 9.7 | 0.2 |
| Feb | 6° / 1° | 178 | 21.2 | 13.3 | 10.6 | 0.3 |
| Mar | 10° / 3° | 145 | 19.6 | 6.5 | 11.7 | 1.6 |
| Apr | 15° / 8° | 97 | 13.4 | 0.4 | 12.9 | 4.3 |
| May | 20° / 13° | 92 | 11.6 | 0 | 14 | 6.1 |
| Jun | 24° / 18° | 115 | 11.5 | 0 | 14.5 | 6.4 |
| Jul | 28° / 22° | 191 | 14.4 | 0 | 14.3 | 5.3 |
| Aug | 30° / 24° | 122 | 12.1 | 0 | 13.4 | 4.9 |
| Sep | 26° / 20° | 162 | 14.1 | 0 | 12.3 | 5.8 |
| Oct | 20° / 14° | 164 | 15.1 | 0 | 11 | 5.6 |
| Nov | 14° / 8° | 180 | 18.5 | 0.3 | 10 | 3.4 |
| Dec | 9° / 4° | 247 | 24.2 | 8.4 | 9.5 | 1.1 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Jōetsu gets about 1946 mm of precipitation a year. On a typical day the chance of rain is very wet, but that rises and falls sharply with the seasons.
The wetter season lasts 4.8 months, from around Nov 6 to Mar 30, peaking in January at about 84% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Jun 3.
January is the wettest month by volume, with 253 mm over about 26 wet days; May is the driest, with 92 mm. Some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 83 | 76 | 63 | 45 | 37 | 39 | 46 | 39 | 48 | 48 | 62 | 78 |
| Rain days | 26 | 21 | 20 | 13 | 12 | 12 | 14 | 12 | 14 | 15 | 19 | 24 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 83 | 26 |
| Feb | 76 | 21 |
| Mar | 63 | 20 |
| Apr | 45 | 13 |
| May | 37 | 12 |
| Jun | 39 | 12 |
| Jul | 46 | 14 |
| Aug | 39 | 12 |
| Sep | 48 | 14 |
| Oct | 48 | 15 |
| Nov | 62 | 19 |
| Dec | 78 | 24 |
Monthly rainfall
Over a full year, Jōetsu collects about 1946 mm of rain across 202 wet days — roughly 162 mm in an average month.
It doesn’t fall evenly. January is the wettest month with 253 mm, while May is the driest at just 92 mm. The three wettest months alone bring about 36% of the year’s total, and some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (mm) | 253 | 178 | 145 | 97 | 92 | 115 | 191 | 122 | 162 | 164 | 180 | 247 |
| Rain days | 26 | 21 | 20 | 13 | 12 | 12 | 14 | 12 | 14 | 15 | 19 | 24 |
| Snow days | 16 | 13 | 7 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 8 |
| Rainfall (mm) | Rain days | Snow days | |
|---|---|---|---|
| Jan | 253 | 26 | 16 |
| Feb | 178 | 21 | 13 |
| Mar | 145 | 20 | 7 |
| Apr | 97 | 13 | 0 |
| May | 92 | 12 | 0 |
| Jun | 115 | 12 | 0 |
| Jul | 191 | 14 | 0 |
| Aug | 122 | 12 | 0 |
| Sep | 162 | 14 | 0 |
| Oct | 164 | 15 | 0 |
| Nov | 180 | 19 | 0 |
| Dec | 247 | 24 | 8 |
Snow in Jōetsu
Average snowy days through the year, the snow-season span, and estimated snowfall — for ski trips and the perennial 'will there be snow at Christmas?' question.
Jōetsu averages about 45 snowy days a year. Snow season runs roughly Nov 19 to Apr 12 — about 4.8 months.
January is snowiest, with roughly 16 days of snow and an estimated 125 cm of snowfall. Over the year that adds up to an estimated 328 cm of snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Snow days | 16 | 13 | 7 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 8 |
| Snowfall (cm) | 125 | 109 | 29 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 64 |
| Snow days | Snowfall (cm) | |
|---|---|---|
| Jan | 16 | 125 |
| Feb | 13 | 109 |
| Mar | 7 | 29 |
| Apr | 0 | 2 |
| May | 0 | 0 |
| Jun | 0 | 0 |
| Jul | 0 | 0 |
| Aug | 0 | 0 |
| Sep | 0 | 0 |
| Oct | 0 | 0 |
| Nov | 0 | 1 |
| Dec | 8 | 64 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Jōetsu, the average share of the sky covered by clouds shows moderate seasonal variation over the course of the year.
The clearer part of the year begins around July 24 and lasts for 3.8 months, ending around November 15. The clearest month is October, when the sky is clear, mostly clear, or partly cloudy 47% of the time on average.
The cloudier part of the year begins around November 16 and lasts for 3.7 months, ending around March 7. The cloudiest month is January, when it is overcast or mostly cloudy 76% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 24 | 31 | 39 | 46 | 45 | 33 | 33 | 46 | 40 | 47 | 38 | 28 |
| Cloudier (%) | 76 | 69 | 61 | 54 | 55 | 67 | 67 | 54 | 60 | 53 | 62 | 72 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 24 | 76 |
| Feb | 31 | 69 |
| Mar | 39 | 61 |
| Apr | 46 | 54 |
| May | 45 | 55 |
| Jun | 33 | 67 |
| Jul | 33 | 67 |
| Aug | 46 | 54 |
| Sep | 40 | 60 |
| Oct | 47 | 53 |
| Nov | 38 | 62 |
| Dec | 28 | 72 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around June 19, brings about 14 h 36 min of light; the shortest, around December 19, only 9 h 24 min — a swing of roughly 5 h 12 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 9.7 | 10.6 | 11.7 | 12.9 | 14.0 | 14.5 | 14.3 | 13.4 | 12.3 | 11.0 | 10.0 | 9.5 |
| Sunrise (AM) | 7:05 | 6:44 | 6:06 | 5:19 | 4:44 | 4:31 | 4:43 | 5:08 | 5:34 | 6:01 | 6:33 | 6:59 |
| Sunset (PM) | 4:48 | 5:19 | 5:48 | 6:16 | 6:43 | 7:03 | 7:02 | 6:34 | 5:48 | 5:03 | 4:32 | 4:27 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 9.7 | 7:05 | 4:48 |
| Feb | 10.6 | 6:44 | 5:19 |
| Mar | 11.7 | 6:06 | 5:48 |
| Apr | 12.9 | 5:19 | 6:16 |
| May | 14.0 | 4:44 | 6:43 |
| Jun | 14.5 | 4:31 | 7:03 |
| Jul | 14.3 | 4:43 | 7:02 |
| Aug | 13.4 | 5:08 | 6:34 |
| Sep | 12.3 | 5:34 | 5:48 |
| Oct | 11.0 | 6:01 | 5:03 |
| Nov | 10.0 | 6:33 | 4:32 |
| Dec | 9.5 | 6:59 | 4:27 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Jōetsu averages about 6 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 1 and 10 days.
The sunnier stretch runs 2.8 months, from around Mar 23 to Jun 14. The sunniest month is April, with roughly 9 sunny days (mixed).
The greyest month is January, down near 2 sunny days — about 83% fewer than the April peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 2 | 3 | 6 | 9 | 9 | 6 | 6 | 9 | 7 | 8 | 6 | 3 |
| Sky | Gloomy | Gloomy | Gloomy | Mixed | Mixed | Gloomy | Gloomy | Mixed | Gloomy | Gloomy | Gloomy | Gloomy |
| Sunny days | Sky | |
|---|---|---|
| Jan | 2 | Gloomy |
| Feb | 3 | Gloomy |
| Mar | 6 | Gloomy |
| Apr | 9 | Mixed |
| May | 9 | Mixed |
| Jun | 6 | Gloomy |
| Jul | 6 | Gloomy |
| Aug | 9 | Mixed |
| Sep | 7 | Gloomy |
| Oct | 8 | Gloomy |
| Nov | 6 | Gloomy |
| Dec | 3 | Gloomy |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
In Jōetsu, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 4.1 months, from around June 4 to October 7. The muggiest month is July, when the air feels humid, muggy or worse about 99% of the time.
The most comfortable stretch runs from around October 8 to June 3, and April is the most comfortable month — the air is dry or comfortable 100% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 100 | 100 | 100 | 97 | 63 | 10 | 0 | 0 | 7 | 58 | 96 | 100 |
| Comfortable (%) | 0 | 0 | 0 | 3 | 29 | 25 | 1 | 1 | 14 | 24 | 4 | 0 |
| Humid (%) | 0 | 0 | 0 | 0 | 7 | 37 | 8 | 5 | 27 | 14 | 0 | 0 |
| Muggy (%) | 0 | 0 | 0 | 0 | 0 | 23 | 35 | 25 | 30 | 3 | 0 | 0 |
| Oppressive (%) | 0 | 0 | 0 | 0 | 0 | 5 | 52 | 61 | 20 | 0 | 0 | 0 |
| Miserable (%) | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 8 | 1 | 0 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|---|---|
| Jan | 100 | 0 | 0 | 0 | 0 | 0 |
| Feb | 100 | 0 | 0 | 0 | 0 | 0 |
| Mar | 100 | 0 | 0 | 0 | 0 | 0 |
| Apr | 97 | 3 | 0 | 0 | 0 | 0 |
| May | 63 | 29 | 7 | 0 | 0 | 0 |
| Jun | 10 | 25 | 37 | 23 | 5 | 0 |
| Jul | 0 | 1 | 8 | 35 | 52 | 3 |
| Aug | 0 | 1 | 5 | 25 | 61 | 8 |
| Sep | 7 | 14 | 27 | 30 | 20 | 1 |
| Oct | 58 | 24 | 14 | 3 | 0 | 0 |
| Nov | 96 | 4 | 0 | 0 | 0 | 0 |
| Dec | 100 | 0 | 0 | 0 | 0 | 0 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in Jōetsu is typically calm, near 11 km/h, and varies moderately with the seasons.
The windier part of the year lasts 5.8 months, from around Oct 29 to Apr 24. The windiest month is January, averaging about 16 km/h (light breeze).
The calmer part of the year runs from around Apr 25 to Oct 28, with July the calmest month at about 8 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 16 | 15 | 13 | 12 | 10 | 8 | 8 | 8 | 9 | 10 | 13 | 15 |
| Feels | light breeze | light breeze | light breeze | calm | calm | calm | calm | calm | calm | calm | light breeze | light breeze |
| Wind speed (km/h) | Feels | |
|---|---|---|
| Jan | 16 | light breeze |
| Feb | 15 | light breeze |
| Mar | 13 | light breeze |
| Apr | 12 | calm |
| May | 10 | calm |
| Jun | 8 | calm |
| Jul | 8 | calm |
| Aug | 8 | calm |
| Sep | 9 | calm |
| Oct | 10 | calm |
| Nov | 13 | light breeze |
| Dec | 15 | light breeze |
Hazard calendar for Jōetsu
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
Jōetsu sits in the Pacific typhoon belt; the season peaks July–October.
Best time to visit Jōetsu
To characterize how pleasant the weather is in Jōetsu throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around late June, Jōetsu is still near the tail of its best-weather window — great conditions with the peak-season crowds already thinning.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 18°C and 28°C. Based on this score, the best times of year to visit Jōetsu for general outdoor tourist activities run from late April to mid July and again from early September to late October, with a peak score in the first week of June.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 0.2 | 0.3 | 1.6 | 4.2 | 6.1 | 6.3 | 5.3 | 4.9 | 5.8 | 5.5 | 3.4 | 1.1 |
| Rating | poor | poor | poor | fair | good | good | fair | fair | good | good | poor | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 0.2 | poor |
| Feb | 0.3 | poor |
| Mar | 1.6 | poor |
| Apr | 4.2 | fair |
| May | 6.1 | good |
| Jun | 6.3 | good |
| Jul | 5.3 | fair |
| Aug | 4.9 | fair |
| Sep | 5.8 | good |
| Oct | 5.5 | good |
| Nov | 3.4 | poor |
| Dec | 1.1 | poor |
The beach/pool score favors clear, rainless days with daytime highs between 24°C and 34°C. Based on this score, the best times of year to visit Jōetsu for hot-weather activities run from mid June to late June and again from early July to mid September, with a peak score in the first week of August.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for Jōetsu, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
For a warm-season trip around August (highs near 30°C), the essentials are light clothes, rain gear and sun protection. In the cold season around January (highs near 6°C), pack a warm layer, a heavy coat and rain gear.
In August, Jōetsu sees daytime highs around 30°C and nights near 24°C. Pack light clothes. Worth having: rain gear and sun protection. About 12 days see rain.
Sea temperature near Jōetsu
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
The sea offshore is warmest in August at about 27°C and coldest in March near 10°C.
It's comfortable for a long swim from Jun 20 to Nov 1 — about 4.4 months when the water holds above 20°C.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 13 | 11 | 10 | 11 | 15 | 20 | 23 | 27 | 25 | 22 | 19 | 15 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Cool | Refreshing | Warm | Warm | Refreshing | Cool | Cool |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 13 | Bracing |
| Feb | 11 | Bracing |
| Mar | 10 | Bracing |
| Apr | 11 | Bracing |
| May | 15 | Bracing |
| Jun | 20 | Cool |
| Jul | 23 | Refreshing |
| Aug | 27 | Warm |
| Sep | 25 | Warm |
| Oct | 22 | Refreshing |
| Nov | 19 | Cool |
| Dec | 15 | Cool |
UV index (midday) in Jōetsu by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
Under clear skies, the midday UV index in Jōetsu peaks around August 12 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 2 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 4 | 4 | 7 | 8 | 9 | 9 | 10 | 9 | 5 | 3 | 2 |
| Level | Moderate | Moderate | Moderate | High | Very high | Very high | Very high | Very high | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Moderate |
| Feb | 4 | Moderate |
| Mar | 4 | Moderate |
| Apr | 7 | High |
| May | 8 | Very high |
| Jun | 9 | Very high |
| Jul | 9 | Very high |
| Aug | 10 | Very high |
| Sep | 9 | Very high |
| Oct | 5 | High |
| Nov | 3 | Moderate |
| Dec | 2 | Moderate |
Average hourly UV index in Jōetsu
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in August the burn window is concentrated in the middle of the day: about 8 hours a day reach index 3 (protection recommended), and 5.5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 0 | 2.5 | 4.5 | 6.5 | 7.5 | 8 | 8 | 8 | 7 | 5 | 0 | 0 |
| UV ≥ 6 (h/day) | 0 | 0 | 0 | 2 | 4.5 | 5 | 5.5 | 5.5 | 4.5 | 0 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 0 | 0 |
| Feb | 2.5 | 0 |
| Mar | 4.5 | 0 |
| Apr | 6.5 | 2 |
| May | 7.5 | 4.5 |
| Jun | 8 | 5 |
| Jul | 8 | 5.5 |
| Aug | 8 | 5.5 |
| Sep | 7 | 4.5 |
| Oct | 5 | 0 |
| Nov | 0 | 0 |
| Dec | 0 | 0 |
Air quality in Jōetsu by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly average.
Air quality in Jōetsu is worst in April — around 22 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (December, 9 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 11 | 14 | 20 | 22 | 20 | 17 | 15 | 12 | 10 | 10 | 10 | 9 |
| Level | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 11 | Good |
| Feb | 14 | Moderate |
| Mar | 20 | Moderate |
| Apr | 22 | Moderate |
| May | 20 | Moderate |
| Jun | 17 | Moderate |
| Jul | 15 | Moderate |
| Aug | 12 | Good |
| Sep | 10 | Good |
| Oct | 10 | Good |
| Nov | 10 | Good |
| Dec | 9 | Good |
Growing season
Jōetsu is mild enough that a frost-free day stays more likely than not even in midwinter. Nights are reliably above freezing from about March 15 to December 22 (283 days); outside that window a hard frost is an occasional risk.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 74 | 68 | 90 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 93 |
| Frost nights | 31 | 28 | 14 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 74 | 31 |
| Feb | 68 | 28 |
| Mar | 90 | 14 |
| Apr | 100 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 100 | 0 |
| Dec | 93 | 3 |
Growing degree days
Growing degree days tally heat above 10°C: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. Jōetsu banks about 2,216 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°C·days) | 0 | 0 | 0 | 48 | 209 | 332 | 465 | 517 | 383 | 218 | 45 | 0 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 0 |
| Feb | 0 |
| Mar | 0 |
| Apr | 48 |
| May | 209 |
| Jun | 332 |
| Jul | 465 |
| Aug | 517 |
| Sep | 383 |
| Oct | 218 |
| Nov | 45 |
| Dec | 0 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
Jōetsu receives about 4.0 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 1.9 and 6.0 kWh/m².
The brighter stretch of the year lasts 6.3 months, from around Mar 9 to Sep 15. The brightest month is May, averaging about 5.8 kWh/m² (bright).
The dimmest month is December, down near 1.9 kWh/m² — roughly 67% less than the May peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 2.3 | 3.2 | 4.3 | 5.3 | 5.8 | 5.5 | 5.1 | 5.2 | 4.0 | 3.2 | 2.3 | 1.9 |
| Level | Moderate | Moderate | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Moderate | Moderate | Dim |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 2.3 | Moderate |
| Feb | 3.2 | Moderate |
| Mar | 4.3 | Bright |
| Apr | 5.3 | Bright |
| May | 5.8 | Bright |
| Jun | 5.5 | Bright |
| Jul | 5.1 | Bright |
| Aug | 5.2 | Bright |
| Sep | 4.0 | Bright |
| Oct | 3.2 | Moderate |
| Nov | 2.3 | Moderate |
| Dec | 1.9 | Dim |
Where is Jōetsu?
Jōetsu sits at 37.1°N, 138.2°E, 10 m above sea level, in Japan. The nearest listed city is Myoko, 14 km away.
Topography around Jōetsu
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Jōetsu.
Within 3 km, the terrain around Jōetsu has only modest variations in elevation — a maximum elevation change of 177 m around an average of 22 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,200 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,900 m.
The land around Jōetsu is covered by artificial surfaces (46%), trees (24%) and cropland (20%) within 3 km, trees (39%) and water (32%) within 16 km, and trees (53%) and water (37%) within 80 km.
Japan travel facts
- Travel advisory
- Level 1
- Exercise Normal Precautions
- Power plugs
- Type A / B
- 100 V · 50 / 60 Hz
- Prices
- ≈ 65% of US
- price level, 2025
- GDP per capita
- $35,951
- 2025
- Happiness
- 6.1 / 10
- World Happiness, 2025
- Safe drinking water
- 99%
- of population, 2024
- Homicide rate
- 0.2
- per 100k, 2023
- Road deaths
- 3.6
- per 100k/yr, 2019
- Income group
- High
- World Bank
- English
- Very low
- EF EPI 446
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Jōetsu (37.1483°, 138.2364°, elevation 10 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).