Karuizawa climate — normals and trends
Karuizawa (Japan) has a hot-summer humid continental climate (Dfa) under the Köppen-Geiger classification. Its mean annual temperature is 9.9 °C and it receives 1,851 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is August (22.0 °C on average) and the coldest is January (-2.4 °C). Rainfall peaks in July.
Karuizawa averages 115 frost days, 4 hot days (≥ 30 °C) and 188 rainy days per year.
Karuizawa has warmed by +3.0 °C between 1940 and 2025, or +0.35 °C per decade. This trend is statistically significant.
The number of frost days there went from about 135 to 95 per year over the period.
The hottest day of the period reached 34.1 °C (on 29 June 2022) and the coldest -20.2 °C (on 15 February 1942).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
KaruizawaNagano
- coords
- 36.35°, 138.63°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
9.9°C
Average daily high
14.2°C
Average daily low
6.1°C
Annual rainfall
1,851mm
Sunshine / day
8.8h
Mean relative humidity
74%
Average peak wind
10.8km/h
Seasonal range
24.4°C
Frost days (< 0 °C)
115 d/yr
Hot days (≥ 30 °C)
4 d/yr
Rainy days (≥ 1 mm)
188 d/yr
Annual snowfall
105.6 cm
Average feels-like high
13.2 °C
Average feels-like low
4.4 °C
Average peak gust
34.5 km/h
Tropical nights (≥ 20 °C)
18 d/yr
Solar radiation
14.6 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+3.0 °C
since 1940
+0.4 °C per decade · r² = 0.71 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
34.1 °C
29 June 2022
Coldest day
-20.2 °C
15 February 1942
Wettest day
279 mm
12 October 2019
Windiest day
40.8 km/h
2 August 1982
Strongest gust
169.2 km/h
27 September 1959
Hottest feels-like
38.6 °C
15 July 2018
Coldest feels-like
-25.0 °C
15 February 1942
Snowiest day
61.1 cm
15 February 2014
Sunniest day
14.0 h
14 June 2004
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 4.7 °C | +2.3 °C | 26 mm | -22 mm |
| Feb | 3.8 °C | +0.7 °C | 22 mm | -39 mm |
| Mar | 9.1 °C | +1.9 °C | 154 mm | +54 mm |
| Apr | 15.7 °C | +2.0 °C | 116 mm | -6 mm |
| May | 18.8 °C | +0.5 °C | 196 mm | +29 mm |
| Jun | 24.5 °C | +3.6 °C | 222 mm | -45 mm |
| Jul | 27.8 °C | +3.0 °C | 280 mm | -12 mm |
| Aug | 28.8 °C | +3.0 °C | 178 mm | -82 mm |
| Sep | 24.9 °C | +3.1 °C | 226 mm | -22 mm |
| Oct | 16.9 °C | +0.7 °C | 155 mm | -13 mm |
| Nov | 11.6 °C | +0.6 °C | 22 mm | -52 mm |
| Dec | 6.9 °C | +1.5 °C | 43 mm | -3 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of Karuizawa?
Karuizawa has a hot-summer humid continental climate (Köppen Dfa). Over 1940-2025, the average annual temperature is 9.9 °C and it receives 1,851 mm of precipitation per year.
What is the hottest day ever recorded in Karuizawa?
The hottest day measured in Karuizawa between 1940 and 2025 was 29 June 2022, reaching 34.1 °C.
What is the coldest day in Karuizawa?
The coldest day measured in Karuizawa between 1940 and 2025 was 15 February 1942, at -20.2 °C.
Does it snow in Karuizawa?
Yes. Karuizawa gets on average 105.6 cm of snow per year and has around 115 frost days.
Has the climate of Karuizawa warmed?
Yes: Karuizawa warmed by +3.0 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Karuizawa?
The wettest day measured in Karuizawa between 1940 and 2025 was 12 October 2019, with 279 mm of rain in 24 hours.
What was the windiest day in Karuizawa?
The windiest day measured in Karuizawa between 1940 and 2025 was 2 August 1982, with winds reaching 40.8 km/h.
What is the warmest month in Karuizawa?
The warmest month in Karuizawa is August (22.0 °C on average); the coldest is January (-2.4 °C).
How much does it rain in Karuizawa?
Karuizawa receives on average 1,851 mm of precipitation per year, spread over about 188 rainy days.
Is it sunny in Karuizawa?
Karuizawa gets on average 8.8 hours of sunshine per day, roughly 3,212 hours per year over 1940-2025.
What is the biggest single-day snowfall in Karuizawa?
The heaviest 24-hour snowfall measured in Karuizawa between 1940 and 2025 was 15 February 2014, with 61.1 cm.
Are there tropical nights in Karuizawa?
Yes: Karuizawa has on average 18 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Karuizawa?
In Karuizawa, between 1940 and 2025, the highest apparent temperature reached 38.6 °C on 15 July 2018, and the lowest was -25.0 °C on 15 February 1942.
Compare Karuizawa with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Karuizawa