Karuizawa weather in February
In February, Karuizawa sees average daytime highs of 4°C and overnight lows near -4°C, with 60 mm of precipitation across 8.6 wet days and about 10.6 hours of daylight. It is the 11th-warmest and 10th-wettest month of the year here.
Highs climb over the month, from about 3°C in the first days to 5°C by the end. The sky is clear or mostly clear about 39% of the time in February, and the air most often feels dry.
Daylight stretches from about 10 h 12 min at the start of February to 11 h 06 min by month's end. Set against the rest of the year, February is Karuizawa's 4th-clearest and 2nd-windiest month. For the whole year in context, see Karuizawa's year-round climate.
- Daytime high
- 4°
- 11th warmest
- Overnight low
- -4°
- 2nd coldest
- Precipitation
- 60 mm
- 8.6 wet days
- Daylight
- 10 h 36 min
- 6:41 AM – 5:19 PM
- Cloud cover
- 52%
- 4th clearest
- Wind
- 9 km/h
- 2nd windiest
- Solar energy
- 3.82 kWh/m²
- Travel score
- 0.0
- out of 10
Temperature in February
Highs climb over the month, from about 3°C in the first days to 5°C by the end.
A typical February day in Karuizawa reaches about 4°C in the afternoon and slips back to -4°C overnight — a 8°C spread between the day's warmth and the night's chill. On most days the high lands between -0°C and 9°C. Set against its neighbours, February runs about 1°C warmer than January and about 4°C cooler than March.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 6 |
| Avg low (°C) | -5 | -5 | -5 | -5 | -5 | -5 | -5 | -5 | -5 | -5 | -5 | -5 | -5 | -4 | -4 | -4 | -4 | -4 | -4 | -4 | -4 | -4 | -4 | -4 | -3 | -3 | -3 | -3 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| 1 | 3 | -5 |
| 2 | 3 | -5 |
| 3 | 3 | -5 |
| 4 | 3 | -5 |
| 5 | 3 | -5 |
| 6 | 3 | -5 |
| 7 | 3 | -5 |
| 8 | 3 | -5 |
| 9 | 4 | -5 |
| 10 | 4 | -5 |
| 11 | 4 | -5 |
| 12 | 4 | -5 |
| 13 | 4 | -5 |
| 14 | 4 | -4 |
| 15 | 4 | -4 |
| 16 | 4 | -4 |
| 17 | 4 | -4 |
| 18 | 4 | -4 |
| 19 | 4 | -4 |
| 20 | 5 | -4 |
| 21 | 5 | -4 |
| 22 | 5 | -4 |
| 23 | 5 | -4 |
| 24 | 5 | -4 |
| 25 | 5 | -3 |
| 26 | 5 | -3 |
| 27 | 5 | -3 |
| 28 | 6 | -3 |
How February really feels in Karuizawa
Once humidity and wind are folded in, February averages 0 days that feel above 32°C and 28 that feel at or below 0°C — the comfort signal a plain temperature reading hides.
The story in February is cold — wind chill drags the overnight "feels like" below the raw low.
Karuizawa weather by month
How February compares with the rest of the year at a glance. February is the 11th-warmest and 10th-wettest month here — the current month is highlighted below.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 3° / -4° | 59 | 7.4 | 6.5 | 9.8 | 0.0 |
| Feb | 4° / -4° | 60 | 8.6 | 6.7 | 10.6 | 0.0 |
| Mar | 8° / -1° | 110 | 13.1 | 7.1 | 11.7 | 1.3 |
| Apr | 14° / 5° | 122 | 13.8 | 2.1 | 12.9 | 3.7 |
| May | 19° / 10° | 165 | 16.8 | 0.1 | 13.9 | 5.1 |
| Jun | 21° / 15° | 254 | 22.7 | 0 | 14.4 | 4.3 |
| Jul | 25° / 19° | 282 | 24 | 0 | 14.2 | 4.5 |
| Aug | 26° / 19° | 240 | 24.1 | 0 | 13.4 | 4.5 |
| Sep | 22° / 16° | 241 | 20.6 | 0 | 12.2 | 4.8 |
| Oct | 17° / 9° | 195 | 15.5 | 0 | 11.1 | 4.7 |
| Nov | 11° / 3° | 72 | 8.8 | 0.6 | 10.1 | 3.1 |
| Dec | 6° / -1° | 49 | 7.6 | 4.4 | 9.6 | 0.6 |
Cloud cover in February
The sky is clear or mostly clear about 39% of the time in February.
Beyond those clear spells, partly cloudy skies cover about 21% of February, with mostly cloudy or overcast conditions the remaining 40%. Skies tend to cloud over as the month goes on.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 65 | 65 | 65 | 65 | 64 | 64 | 63 | 62 | 62 | 62 | 62 | 60 | 60 | 60 | 59 | 59 | 59 | 58 | 58 | 57 | 57 | 57 | 57 | 57 | 57 | 56 | 56 | 56 |
| Cloudier (%) | 35 | 35 | 35 | 35 | 36 | 36 | 37 | 38 | 38 | 38 | 38 | 40 | 40 | 40 | 41 | 41 | 41 | 42 | 42 | 43 | 43 | 43 | 43 | 43 | 43 | 44 | 44 | 44 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| 1 | 65 | 35 |
| 2 | 65 | 35 |
| 3 | 65 | 35 |
| 4 | 65 | 35 |
| 5 | 64 | 36 |
| 6 | 64 | 36 |
| 7 | 63 | 37 |
| 8 | 62 | 38 |
| 9 | 62 | 38 |
| 10 | 62 | 38 |
| 11 | 62 | 38 |
| 12 | 60 | 40 |
| 13 | 60 | 40 |
| 14 | 60 | 40 |
| 15 | 59 | 41 |
| 16 | 59 | 41 |
| 17 | 59 | 41 |
| 18 | 58 | 42 |
| 19 | 58 | 42 |
| 20 | 57 | 43 |
| 21 | 57 | 43 |
| 22 | 57 | 43 |
| 23 | 57 | 43 |
| 24 | 57 | 43 |
| 25 | 57 | 43 |
| 26 | 56 | 44 |
| 27 | 56 | 44 |
| 28 | 56 | 44 |
Chance of precipitation in February
Karuizawa gets around 60 mm of rain and snow over 8.6 wet days in February. The line is the day-by-day chance of measurable precipitation.
Day to day, the chance of measurable precipitation averages around 31% and peaks near 37% on the wettest days, and about 7 days bring snow. The odds climb toward the end of the month.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain chance (%) | 26 | 27 | 27 | 27 | 28 | 28 | 29 | 29 | 30 | 30 | 30 | 31 | 31 | 31 | 31 | 31 | 32 | 32 | 32 | 32 | 33 | 33 | 34 | 35 | 35 | 36 | 36 | 37 |
| Snow chance (%) | 22 | 22 | 22 | 22 | 22 | 22 | 23 | 23 | 24 | 24 | 24 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 26 | 26 | 26 | 26 | 26 | 26 |
| Rain chance (%) | Snow chance (%) | |
|---|---|---|
| 1 | 26 | 22 |
| 2 | 27 | 22 |
| 3 | 27 | 22 |
| 4 | 27 | 22 |
| 5 | 28 | 22 |
| 6 | 28 | 22 |
| 7 | 29 | 23 |
| 8 | 29 | 23 |
| 9 | 30 | 24 |
| 10 | 30 | 24 |
| 11 | 30 | 24 |
| 12 | 31 | 25 |
| 13 | 31 | 25 |
| 14 | 31 | 25 |
| 15 | 31 | 25 |
| 16 | 31 | 25 |
| 17 | 32 | 25 |
| 18 | 32 | 25 |
| 19 | 32 | 25 |
| 20 | 32 | 25 |
| 21 | 33 | 25 |
| 22 | 33 | 25 |
| 23 | 34 | 26 |
| 24 | 35 | 26 |
| 25 | 35 | 26 |
| 26 | 36 | 26 |
| 27 | 36 | 26 |
| 28 | 37 | 26 |
Humidity in February
Most of February feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
By dew point, February lands in the dry band about 100% of days. It rarely turns muggy — the humid and sticky bands barely register.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Dry (%) | |
|---|---|
| 1 | 100 |
| 2 | 100 |
| 3 | 100 |
| 4 | 100 |
| 5 | 100 |
| 6 | 100 |
| 7 | 100 |
| 8 | 100 |
| 9 | 100 |
| 10 | 100 |
| 11 | 100 |
| 12 | 100 |
| 13 | 100 |
| 14 | 100 |
| 15 | 100 |
| 16 | 100 |
| 17 | 100 |
| 18 | 100 |
| 19 | 100 |
| 20 | 100 |
| 21 | 100 |
| 22 | 100 |
| 23 | 100 |
| 24 | 100 |
| 25 | 100 |
| 26 | 100 |
| 27 | 100 |
| 28 | 100 |
Wind in February
Winds average 9 km/h in February.
Across February, daily wind ranges from about 8 km/h on the calmest days to 9 km/h at its breeziest. It stays fairly steady from day to day.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 8 | 8 | 8 | 8 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (km/h) | Feels | |
|---|---|---|
| 1 | 9 | calm |
| 2 | 9 | calm |
| 3 | 9 | calm |
| 4 | 9 | calm |
| 5 | 9 | calm |
| 6 | 9 | calm |
| 7 | 9 | calm |
| 8 | 9 | calm |
| 9 | 9 | calm |
| 10 | 9 | calm |
| 11 | 9 | calm |
| 12 | 9 | calm |
| 13 | 9 | calm |
| 14 | 9 | calm |
| 15 | 9 | calm |
| 16 | 9 | calm |
| 17 | 9 | calm |
| 18 | 9 | calm |
| 19 | 9 | calm |
| 20 | 9 | calm |
| 21 | 9 | calm |
| 22 | 9 | calm |
| 23 | 9 | calm |
| 24 | 9 | calm |
| 25 | 8 | calm |
| 26 | 8 | calm |
| 27 | 8 | calm |
| 28 | 8 | calm |
Sunrise & sunset in February
Daylight runs from about 10 h 12 min at the start of February to 11 h 06 min by month's end. The lit band spans sunrise to sunset each day.
Days grow by about 54 minutes over February. Sunrise moves from 6:54 AM to 6:26 AM, and sunset from 5:04 PM to 5:32 PM.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 10.2 | 10.2 | 10.2 | 10.3 | 10.3 | 10.3 | 10.4 | 10.4 | 10.4 | 10.5 | 10.5 | 10.5 | 10.6 | 10.6 | 10.6 | 10.7 | 10.7 | 10.7 | 10.8 | 10.8 | 10.8 | 10.9 | 10.9 | 10.9 | 11.0 | 11.0 | 11.1 | 11.1 |
| Sunrise (AM) | 6:54 | 6:53 | 6:52 | 6:52 | 6:51 | 6:50 | 6:49 | 6:48 | 6:47 | 6:46 | 6:45 | 6:44 | 6:43 | 6:42 | 6:41 | 6:40 | 6:39 | 6:38 | 6:37 | 6:36 | 6:35 | 6:34 | 6:32 | 6:31 | 6:30 | 6:29 | 6:27 | 6:26 |
| Sunset (PM) | 5:04 | 5:05 | 5:06 | 5:07 | 5:08 | 5:09 | 5:10 | 5:11 | 5:13 | 5:14 | 5:15 | 5:16 | 5:17 | 5:18 | 5:19 | 5:20 | 5:21 | 5:22 | 5:23 | 5:24 | 5:25 | 5:26 | 5:27 | 5:28 | 5:29 | 5:30 | 5:31 | 5:32 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| 1 | 10.2 | 6:54 | 5:04 |
| 2 | 10.2 | 6:53 | 5:05 |
| 3 | 10.2 | 6:52 | 5:06 |
| 4 | 10.3 | 6:52 | 5:07 |
| 5 | 10.3 | 6:51 | 5:08 |
| 6 | 10.3 | 6:50 | 5:09 |
| 7 | 10.4 | 6:49 | 5:10 |
| 8 | 10.4 | 6:48 | 5:11 |
| 9 | 10.4 | 6:47 | 5:13 |
| 10 | 10.5 | 6:46 | 5:14 |
| 11 | 10.5 | 6:45 | 5:15 |
| 12 | 10.5 | 6:44 | 5:16 |
| 13 | 10.6 | 6:43 | 5:17 |
| 14 | 10.6 | 6:42 | 5:18 |
| 15 | 10.6 | 6:41 | 5:19 |
| 16 | 10.7 | 6:40 | 5:20 |
| 17 | 10.7 | 6:39 | 5:21 |
| 18 | 10.7 | 6:38 | 5:22 |
| 19 | 10.8 | 6:37 | 5:23 |
| 20 | 10.8 | 6:36 | 5:24 |
| 21 | 10.8 | 6:35 | 5:25 |
| 22 | 10.9 | 6:34 | 5:26 |
| 23 | 10.9 | 6:32 | 5:27 |
| 24 | 10.9 | 6:31 | 5:28 |
| 25 | 11.0 | 6:30 | 5:29 |
| 26 | 11.0 | 6:29 | 5:30 |
| 27 | 11.1 | 6:27 | 5:31 |
| 28 | 11.1 | 6:26 | 5:32 |
Solar energy in February
Average shortwave solar energy reaching the ground each day in February, about 3.82 kWh/m².
For context, solar energy here swings from a low near 2.51 kWh/m² to a high of 5.52 kWh/m² in May across the year — February's 3.82 kWh/m² falls in the middle.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 3.4 | 3.4 | 3.5 | 3.5 | 3.5 | 3.6 | 3.6 | 3.6 | 3.6 | 3.7 | 3.7 | 3.7 | 3.8 | 3.8 | 3.8 | 3.9 | 3.9 | 3.9 | 3.9 | 4.0 | 4.0 | 4.0 | 4.0 | 4.1 | 4.1 | 4.1 | 4.2 | 4.2 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| 1 | 3.4 | Moderate |
| 2 | 3.4 | Moderate |
| 3 | 3.5 | Moderate |
| 4 | 3.5 | Moderate |
| 5 | 3.5 | Moderate |
| 6 | 3.6 | Moderate |
| 7 | 3.6 | Moderate |
| 8 | 3.6 | Moderate |
| 9 | 3.6 | Moderate |
| 10 | 3.7 | Moderate |
| 11 | 3.7 | Moderate |
| 12 | 3.7 | Moderate |
| 13 | 3.8 | Moderate |
| 14 | 3.8 | Moderate |
| 15 | 3.8 | Moderate |
| 16 | 3.9 | Moderate |
| 17 | 3.9 | Moderate |
| 18 | 3.9 | Moderate |
| 19 | 3.9 | Moderate |
| 20 | 4.0 | Moderate |
| 21 | 4.0 | Bright |
| 22 | 4.0 | Bright |
| 23 | 4.0 | Bright |
| 24 | 4.1 | Bright |
| 25 | 4.1 | Bright |
| 26 | 4.1 | Bright |
| 27 | 4.2 | Bright |
| 28 | 4.2 | Bright |
Hazard calendar for Karuizawa
None of Karuizawa's seasonal hazards are active in February. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.
Karuizawa's rainy season runs May–October, when most of the year's rain falls.
Is February a good time to visit Karuizawa?
Our two travel scores rate February for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).
February is a weaker month for outdoor sightseeing in Karuizawa.
What to pack for Karuizawa in February
From February's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In February, Karuizawa sees daytime highs around 4°C and nights near -4°C. Pack a warm layer and a heavy coat. Worth having: rain gear. About 9 days see rain.
UV index in Karuizawa in February
Clear-sky midday UV in February peaks around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Karuizawa peaks around July 18 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 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 | 6 | 7 | 8 | 9 | 10 | 9 | 9 | 6 | 3 | 2 |
| Level | Moderate | Moderate | High | 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 | 6 | High |
| Apr | 7 | High |
| May | 8 | Very high |
| Jun | 9 | Very high |
| Jul | 10 | Very high |
| Aug | 9 | Very high |
| Sep | 9 | Very high |
| Oct | 6 | High |
| Nov | 3 | Moderate |
| Dec | 2 | Moderate |
Air quality in Karuizawa in February
Average fine-particle pollution (PM2.5) through the year — so you can see where February falls, not just the annual average.
Air quality in Karuizawa is worst in April — around 21 µg/m³ PM2.5 (moderate), about 2.2× 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) | 11 | 14 | 19 | 21 | 20 | 18 | 15 | 14 | 13 | 12 | 11 | 10 |
| Level | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 11 | Good |
| Feb | 14 | Moderate |
| Mar | 19 | Moderate |
| Apr | 21 | Moderate |
| May | 20 | Moderate |
| Jun | 18 | Moderate |
| Jul | 15 | Moderate |
| Aug | 14 | Moderate |
| Sep | 13 | Moderate |
| Oct | 12 | Moderate |
| Nov | 11 | Good |
| Dec | 10 | Good |
Where is Karuizawa?
Karuizawa sits at 36.4°N, 138.6°E, 952 m above sea level, in Japan. The nearest listed city is Miyota, 11 km away.
Topography around Karuizawa
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Karuizawa.
Within 3 km, the terrain around Karuizawa has large variations in elevation — a maximum elevation change of 632 m around an average of 1,004 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 2,316 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,985 m.
The land around Karuizawa is covered by trees (86%) within 3 km, trees (86%) within 16 km, and trees (80%) 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 Karuizawa (36.35°, 138.6333°, elevation 952 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. 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).