Climate and average weather in Uonuma
In Uonuma, the summers are humid, hot, wet, and partly cloudy and the winters are cold, snowy, and mostly cloudy.
Over the course of the year, the temperature in Uonuma typically varies from -3°C to 28°C, and is rarely below -7°C or above 33°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 Uonuma for warm-weather activities are from late April to early July and mid August to late October.
- Hottest
- Aug
- 28°
- Coldest
- Jan
- -3°
- Wettest
- Jan
- 298 mm
- Driest
- Apr
- 143 mm
- Rain / yr
- 2486 mm
- 232 wet days
- Daylight
- 9.4–14.6 h
- shortest–longest
- Elevation
- 95 m
- 37.2°N
- Clearest
- Apr
- 64% cloud
Uonuma is city in Niigata Prefecture, Japan.
- Density
- 36/km²
- people per km²
- Founded
- 2004
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Uonuma 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 mid August to late October.
Temperature through the year
Daily average highs and lows in Uonuma, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 3.8 months, from June 2 to September 25, with daily high temperatures above 22°C. The hottest month of the year in Uonuma is August, with an average high of 28°C and low of 21°C.
The cool season lasts 3.5 months, from December 5 to March 20, with daily high temperatures below 7°C. The coldest month of the year in Uonuma is January, with an average low of -3°C and high of 2°C.
Days typically run about 8°C warmer than nights, with the widest day–night swing (around 10°C) in April.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 2 | 3 | 7 | 14 | 20 | 23 | 27 | 28 | 24 | 18 | 12 | 5 |
| Avg low (°C) | -3 | -3 | -1 | 4 | 10 | 15 | 20 | 21 | 17 | 10 | 4 | -1 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 2 | -3 |
| Feb | 3 | -3 |
| Mar | 7 | -1 |
| Apr | 14 | 4 |
| May | 20 | 10 |
| Jun | 23 | 15 |
| Jul | 27 | 20 |
| Aug | 28 | 21 |
| Sep | 24 | 17 |
| Oct | 18 | 10 |
| Nov | 12 | 4 |
| Dec | 5 | -1 |
How hot and cold Uonuma 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 coldest nights, wind chill pulls the feels-like down to about -7°C (around January 25), with roughly 138 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) | 2 | 3 | 7 | 14 | 20 | 23 | 28 | 30 | 24 | 18 | 12 | 5 |
| Air high (°C) | 2 | 3 | 7 | 14 | 20 | 23 | 27 | 28 | 24 | 18 | 12 | 5 |
| Feels-like low (°C) | -7 | -6 | -4 | 2 | 10 | 15 | 20 | 20 | 17 | 10 | 2 | -5 |
| Air low (°C) | -3 | -3 | -1 | 4 | 10 | 15 | 20 | 21 | 17 | 10 | 4 | -1 |
| Feels-like high (°C) | Air high (°C) | Feels-like low (°C) | Air low (°C) | |
|---|---|---|---|---|
| Jan | 2 | 2 | -7 | -3 |
| Feb | 3 | 3 | -6 | -3 |
| Mar | 7 | 7 | -4 | -1 |
| Apr | 14 | 14 | 2 | 4 |
| May | 20 | 20 | 10 | 10 |
| Jun | 23 | 23 | 15 | 15 |
| Jul | 28 | 27 | 20 | 20 |
| Aug | 30 | 28 | 20 | 21 |
| Sep | 24 | 24 | 17 | 17 |
| Oct | 18 | 18 | 10 | 10 |
| Nov | 12 | 12 | 2 | 4 |
| Dec | 5 | 5 | -5 | -1 |
Average hourly temperature in Uonuma
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 28°C, and coldest before dawn in January, near -3°C.
Uonuma 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 | 2° / -3° | 298 | 26.2 | 24.1 | 9.7 | 0.0 |
| Feb | 3° / -3° | 223 | 22 | 19.8 | 10.6 | 0.0 |
| Mar | 7° / -1° | 201 | 21.6 | 14.8 | 11.7 | 0.6 |
| Apr | 14° / 4° | 143 | 16.4 | 3.6 | 12.9 | 3.4 |
| May | 20° / 10° | 152 | 15 | 0.1 | 14 | 5.5 |
| Jun | 23° / 15° | 178 | 16.6 | 0 | 14.5 | 5.5 |
| Jul | 27° / 20° | 263 | 20.5 | 0 | 14.3 | 4.7 |
| Aug | 28° / 21° | 180 | 17.8 | 0 | 13.4 | 4.9 |
| Sep | 24° / 17° | 190 | 16.6 | 0 | 12.3 | 5.5 |
| Oct | 18° / 10° | 196 | 16.6 | 0 | 11 | 4.9 |
| Nov | 12° / 4° | 192 | 18.8 | 3.9 | 10 | 2.5 |
| Dec | 5° / -2° | 271 | 24 | 17.6 | 9.5 | 0.2 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Uonuma gets about 2486 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 4.4 months, from around Nov 16 to Mar 29, peaking in January at about 85% chance on a given day. The drier stretch runs the rest of the year, bottoming out around May 31.
January is the wettest month by volume, with 298 mm over about 26 wet days; April is the driest, with 143 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 (%) | 84 | 79 | 69 | 55 | 48 | 56 | 66 | 57 | 56 | 53 | 63 | 77 |
| Rain days | 26 | 22 | 22 | 16 | 15 | 17 | 21 | 18 | 17 | 17 | 19 | 24 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 84 | 26 |
| Feb | 79 | 22 |
| Mar | 69 | 22 |
| Apr | 55 | 16 |
| May | 48 | 15 |
| Jun | 56 | 17 |
| Jul | 66 | 21 |
| Aug | 57 | 18 |
| Sep | 56 | 17 |
| Oct | 53 | 17 |
| Nov | 63 | 19 |
| Dec | 77 | 24 |
Monthly rainfall
Over a full year, Uonuma collects about 2486 mm of rain across 232 wet days — roughly 207 mm in an average month.
It doesn’t fall evenly. January is the wettest month with 298 mm, while April is the driest at just 143 mm. The three wettest months alone bring about 33% 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) | 298 | 223 | 201 | 143 | 152 | 178 | 263 | 180 | 190 | 196 | 192 | 271 |
| Rain days | 26 | 22 | 22 | 16 | 15 | 17 | 21 | 18 | 17 | 17 | 19 | 24 |
| Snow days | 24 | 20 | 15 | 4 | 0 | 0 | 0 | 0 | 0 | 0 | 4 | 18 |
| Rainfall (mm) | Rain days | Snow days | |
|---|---|---|---|
| Jan | 298 | 26 | 24 |
| Feb | 223 | 22 | 20 |
| Mar | 201 | 22 | 15 |
| Apr | 143 | 16 | 4 |
| May | 152 | 15 | 0 |
| Jun | 178 | 17 | 0 |
| Jul | 263 | 21 | 0 |
| Aug | 180 | 18 | 0 |
| Sep | 190 | 17 | 0 |
| Oct | 196 | 17 | 0 |
| Nov | 192 | 19 | 4 |
| Dec | 271 | 24 | 18 |
Snow in Uonuma
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.
Uonuma averages about 84 snowy days a year. Snow season runs roughly Oct 29 to May 1 — about 6.1 months.
January is snowiest, with roughly 24 days of snow and an estimated 248 cm of snowfall. Over the year that adds up to an estimated 806 cm of snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Snow days | 24 | 20 | 15 | 4 | 0 | 0 | 0 | 0 | 0 | 0 | 4 | 18 |
| Snowfall (cm) | 248 | 223 | 112 | 15 | 0 | 0 | 0 | 0 | 0 | 0 | 25 | 182 |
| Snow days | Snowfall (cm) | |
|---|---|---|
| Jan | 24 | 248 |
| Feb | 20 | 223 |
| Mar | 15 | 112 |
| Apr | 4 | 15 |
| May | 0 | 0 |
| Jun | 0 | 0 |
| Jul | 0 | 0 |
| Aug | 0 | 0 |
| Sep | 0 | 0 |
| Oct | 0 | 0 |
| Nov | 4 | 25 |
| Dec | 18 | 182 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Uonuma, 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 March 20 and lasts for 2.7 months, ending around June 8. The clearest month is April, when the sky is clear, mostly clear, or partly cloudy 40% of the time on average.
The cloudier part of the year begins around November 24 and lasts for 3.8 months, ending around March 19. The cloudiest month is January, when it is overcast or mostly cloudy 85% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 15 | 19 | 29 | 40 | 37 | 25 | 27 | 39 | 34 | 36 | 33 | 23 |
| Cloudier (%) | 85 | 81 | 71 | 60 | 63 | 75 | 73 | 61 | 66 | 64 | 67 | 77 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 15 | 85 |
| Feb | 19 | 81 |
| Mar | 29 | 71 |
| Apr | 40 | 60 |
| May | 37 | 63 |
| Jun | 25 | 75 |
| Jul | 27 | 73 |
| Aug | 39 | 61 |
| Sep | 34 | 66 |
| Oct | 36 | 64 |
| Nov | 33 | 67 |
| Dec | 23 | 77 |
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 17, brings about 14 h 36 min of light; the shortest, around December 16, 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) | 7:02 | 6:41 | 6:03 | 5:16 | 4:41 | 4:28 | 4:40 | 5:05 | 5:31 | 5:58 | 6:30 | 6:57 |
| Sunset (PM) | 4:44 | 5:16 | 5:45 | 6:13 | 6:40 | 7:01 | 7:00 | 6:31 | 5:46 | 5:00 | 4:28 | 4:24 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 9.7 | 7:02 | 4:44 |
| Feb | 10.6 | 6:41 | 5:16 |
| Mar | 11.7 | 6:03 | 5:45 |
| Apr | 12.9 | 5:16 | 6:13 |
| May | 14.0 | 4:41 | 6:40 |
| Jun | 14.5 | 4:28 | 7:01 |
| Jul | 14.3 | 4:40 | 7:00 |
| Aug | 13.4 | 5:05 | 6:31 |
| Sep | 12.3 | 5:31 | 5:46 |
| Oct | 11.0 | 5:58 | 5:00 |
| Nov | 10.0 | 6:30 | 4:28 |
| Dec | 9.5 | 6:57 | 4:24 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Uonuma averages about 5 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 1 and 8 days.
The sunnier stretch runs 2.8 months, from around Mar 18 to Jun 9. The sunniest month is April, with roughly 8 sunny days (gloomy).
The greyest month is January, down near 2 sunny days — about 79% fewer than the April peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 2 | 2 | 5 | 8 | 8 | 4 | 4 | 7 | 5 | 6 | 6 | 3 |
| Sky | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy |
| Sunny days | Sky | |
|---|---|---|
| Jan | 2 | Gloomy |
| Feb | 2 | Gloomy |
| Mar | 5 | Gloomy |
| Apr | 8 | Gloomy |
| May | 8 | Gloomy |
| Jun | 4 | Gloomy |
| Jul | 4 | Gloomy |
| Aug | 7 | Gloomy |
| Sep | 5 | Gloomy |
| Oct | 6 | 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 Uonuma, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 3.7 months, from around June 10 to September 29. The muggiest month is August, when the air feels humid, muggy or worse about 98% of the time.
The most comfortable stretch runs from around September 30 to June 9, 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 | 99 | 82 | 22 | 0 | 0 | 15 | 74 | 99 | 100 |
| Comfortable (%) | 0 | 0 | 0 | 1 | 15 | 34 | 4 | 2 | 22 | 19 | 1 | 0 |
| Humid (%) | 0 | 0 | 0 | 0 | 2 | 30 | 20 | 13 | 30 | 6 | 0 | 0 |
| Muggy (%) | 0 | 0 | 0 | 0 | 0 | 14 | 52 | 48 | 28 | 1 | 0 | 0 |
| Oppressive (%) | 0 | 0 | 0 | 0 | 0 | 1 | 24 | 37 | 5 | 0 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | Oppressive (%) | |
|---|---|---|---|---|---|
| Jan | 100 | 0 | 0 | 0 | 0 |
| Feb | 100 | 0 | 0 | 0 | 0 |
| Mar | 100 | 0 | 0 | 0 | 0 |
| Apr | 99 | 1 | 0 | 0 | 0 |
| May | 82 | 15 | 2 | 0 | 0 |
| Jun | 22 | 34 | 30 | 14 | 1 |
| Jul | 0 | 4 | 20 | 52 | 24 |
| Aug | 0 | 2 | 13 | 48 | 37 |
| Sep | 15 | 22 | 30 | 28 | 5 |
| Oct | 74 | 19 | 6 | 1 | 0 |
| Nov | 99 | 1 | 0 | 0 | 0 |
| Dec | 100 | 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 Uonuma is typically calm, near 7 km/h, and varies little with the seasons.
The windier part of the year lasts 6.4 months, from around Nov 3 to May 15. The windiest month is January, averaging about 8 km/h (calm).
The calmer part of the year runs from around May 16 to Nov 2, with July the calmest month at about 5 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 8 | 9 | 8 | 8 | 7 | 6 | 5 | 5 | 6 | 6 | 7 | 8 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (km/h) | Feels | |
|---|---|---|
| Jan | 8 | calm |
| Feb | 9 | calm |
| Mar | 8 | calm |
| Apr | 8 | calm |
| May | 7 | calm |
| Jun | 6 | calm |
| Jul | 5 | calm |
| Aug | 5 | calm |
| Sep | 6 | calm |
| Oct | 6 | calm |
| Nov | 7 | calm |
| Dec | 8 | calm |
Hazard calendar for Uonuma
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
Uonuma sits in the Pacific typhoon belt; the season peaks July–October.
Best time to visit Uonuma
To characterize how pleasant the weather is in Uonuma throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around mid October, Uonuma 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 Uonuma for general outdoor tourist activities run from late April to early July and again from mid July 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) | 0.0 | 0.0 | 0.7 | 3.4 | 5.5 | 5.5 | 4.7 | 4.9 | 5.5 | 4.9 | 2.5 | 0.3 |
| Rating | poor | poor | poor | poor | good | fair | fair | fair | fair | fair | poor | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 0.0 | poor |
| Feb | 0.0 | poor |
| Mar | 0.7 | poor |
| Apr | 3.4 | poor |
| May | 5.5 | good |
| Jun | 5.5 | fair |
| Jul | 4.7 | fair |
| Aug | 4.9 | fair |
| Sep | 5.5 | fair |
| Oct | 4.9 | fair |
| Nov | 2.5 | poor |
| Dec | 0.3 | poor |
The beach/pool score favors clear, rainless days with daytime highs between 24°C and 34°C. Based on this score, the best time of year to visit Uonuma for hot-weather activities is from mid 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 Uonuma, 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 28°C), the essentials are light clothes, rain gear and sun protection. In the cold season around January (highs near 2°C), pack a warm layer, a heavy coat and rain gear.
In August, Uonuma sees daytime highs around 28°C and nights near 21°C. Pack light clothes and rain gear. Worth having: sun protection. About 18 days see rain.
Sea temperature near Uonuma
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
The sea at the nearest coast (about 33 km away) is warmest in August at about 27°C and coldest in March near 10°C.
It's comfortable for a long swim from Jun 21 to Oct 31 — 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) | 12 | 11 | 10 | 11 | 15 | 20 | 23 | 27 | 25 | 22 | 18 | 15 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Cool | Refreshing | Warm | Warm | Refreshing | Cool | Cool |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 12 | 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 | 18 | Cool |
| Dec | 15 | Cool |
UV index (midday) in Uonuma 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 Uonuma peaks around August 12 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 2 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 4 | 5 | 7 | 8 | 9 | 10 | 10 | 8 | 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 | 5 | Moderate |
| Apr | 7 | High |
| May | 8 | Very high |
| Jun | 9 | Very high |
| Jul | 10 | Very high |
| Aug | 10 | Very high |
| Sep | 8 | Very high |
| Oct | 5 | High |
| Nov | 3 | Moderate |
| Dec | 2 | Moderate |
Average hourly UV index in Uonuma
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 | 3 | 4.5 | 6.5 | 8 | 8.5 | 8.5 | 8 | 7 | 5 | 1.5 | 0 |
| UV ≥ 6 (h/day) | 0 | 0 | 0 | 2.5 | 4.5 | 5.5 | 5.5 | 5.5 | 4 | 0 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 0 | 0 |
| Feb | 3 | 0 |
| Mar | 4.5 | 0 |
| Apr | 6.5 | 2.5 |
| May | 8 | 4.5 |
| Jun | 8.5 | 5.5 |
| Jul | 8.5 | 5.5 |
| Aug | 8 | 5.5 |
| Sep | 7 | 4 |
| Oct | 5 | 0 |
| Nov | 1.5 | 0 |
| Dec | 0 | 0 |
Air quality in Uonuma 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 Uonuma is worst in April — around 23 µg/m³ PM2.5 (moderate), about 2.3× the cleanest month (December, 10 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) | 12 | 15 | 22 | 23 | 22 | 19 | 17 | 14 | 12 | 12 | 11 | 10 |
| Level | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 12 | Good |
| Feb | 15 | Moderate |
| Mar | 22 | Moderate |
| Apr | 23 | Moderate |
| May | 22 | Moderate |
| Jun | 19 | Moderate |
| Jul | 17 | Moderate |
| Aug | 14 | Moderate |
| Sep | 12 | Moderate |
| Oct | 12 | Good |
| Nov | 11 | Good |
| Dec | 10 | Good |
Growing season
The growing season in Uonuma typically lasts about 253 days, from around March 27 to December 4 — the span where a frost-free day is more likely than not. It is reliably frost-free from April 18 to November 12.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 9 | 10 | 35 | 85 | 100 | 100 | 100 | 100 | 100 | 100 | 83 | 30 |
| Frost nights | 31 | 28 | 31 | 17 | 0 | 0 | 0 | 0 | 0 | 0 | 18 | 31 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 9 | 31 |
| Feb | 10 | 28 |
| Mar | 35 | 31 |
| Apr | 85 | 17 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 83 | 18 |
| Dec | 30 | 31 |
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. Uonuma banks about 1,748 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 | 13 | 160 | 281 | 407 | 443 | 311 | 130 | 2 | 0 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 0 |
| Feb | 0 |
| Mar | 0 |
| Apr | 13 |
| May | 160 |
| Jun | 281 |
| Jul | 407 |
| Aug | 443 |
| Sep | 311 |
| Oct | 130 |
| Nov | 2 |
| 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.
Uonuma receives about 3.8 kWh/m² a day of solar energy on average — moderate — with a clear seasonal swing between 1.9 and 5.7 kWh/m².
The brighter stretch of the year lasts 6.3 months, from around Mar 7 to Sep 15. The brightest month is May, averaging about 5.6 kWh/m² (bright).
The dimmest month is December, down near 1.9 kWh/m² — roughly 66% less than the May peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 2.2 | 3.0 | 4.2 | 5.2 | 5.5 | 5.2 | 4.8 | 4.9 | 3.9 | 3.0 | 2.3 | 1.9 |
| Level | Moderate | Moderate | Bright | Bright | Bright | Bright | Bright | Bright | Moderate | Moderate | Moderate | Dim |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 2.2 | Moderate |
| Feb | 3.0 | Moderate |
| Mar | 4.2 | Bright |
| Apr | 5.2 | Bright |
| May | 5.5 | Bright |
| Jun | 5.2 | Bright |
| Jul | 4.8 | Bright |
| Aug | 4.9 | Bright |
| Sep | 3.9 | Moderate |
| Oct | 3.0 | Moderate |
| Nov | 2.3 | Moderate |
| Dec | 1.9 | Dim |
Where is Uonuma?
Uonuma sits at 37.2°N, 139.0°E, 95 m above sea level, in Japan. The nearest listed city is Ojiya, 16 km away.
Topography around Uonuma
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Uonuma.
Within 3 km, the terrain around Uonuma has significant variations in elevation — a maximum elevation change of 251 m around an average of 138 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,713 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,554 m.
The land around Uonuma is covered by trees (43%), cropland (29%) and artificial surfaces (21%) within 3 km, trees (82%) within 16 km, and trees (70%) 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 Uonuma (37.2449°, 138.9623°, elevation 95 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).