Ōmachi climate — normals and trends
Ōmachi (Japan) has a warm-summer humid continental climate (Dfb) under the Köppen-Geiger classification. Its mean annual temperature is 5.2 °C and it receives 3,042 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 (18.9 °C on average) and the coldest is January (-8.4 °C). Rainfall peaks in July.
Ōmachi averages 168 frost days, 0 hot days (≥ 30 °C) and 240 rainy days per year.
Ōmachi has warmed by +2.7 °C between 1940 and 2025, or +0.32 °C per decade. This trend is statistically significant.
The number of frost days there went from about 182 to 154 per year over the period.
The hottest day of the period reached 28.5 °C (on 5 August 2018) and the coldest -23.8 °C (on 14 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
ŌmachiNagano
- coords
- 36.50°, 137.87°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
5.2°C
Average daily high
9.1°C
Average daily low
1.5°C
Annual rainfall
3,042mm
Sunshine / day
8.7h
Mean relative humidity
81%
Average peak wind
8.4km/h
Seasonal range
27.3°C
Frost days (< 0 °C)
168 d/yr
Hot days (≥ 30 °C)
0 d/yr
Rainy days (≥ 1 mm)
240 d/yr
Annual snowfall
524.0 cm
Average feels-like high
7.7 °C
Average feels-like low
-0.8 °C
Average peak gust
40.7 km/h
Tropical nights (≥ 20 °C)
0 d/yr
Solar radiation
14.9 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+2.7 °C
since 1940
+0.3 °C per decade · r² = 0.62 · 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
28.5 °C
5 August 2018
Coldest day
-23.8 °C
14 February 1942
Wettest day
202 mm
14 August 2021
Windiest day
37.3 km/h
16 September 1961
Strongest gust
184.7 km/h
27 September 1959
Hottest feels-like
33.0 °C
8 August 2019
Coldest feels-like
-28.6 °C
14 February 1942
Snowiest day
36.7 cm
15 February 2014
Sunniest day
14.0 h
11 June 1940
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 | -4.4 °C | +0.8 °C | 164 mm | -15 mm |
| Feb | -3.9 °C | +0.2 °C | 163 mm | +0 mm |
| Mar | 2.8 °C | +2.6 °C | 221 mm | +23 mm |
| Apr | 8.4 °C | +1.7 °C | 169 mm | -30 mm |
| May | 15.0 °C | +1.3 °C | 236 mm | +1 mm |
| Jun | 20.3 °C | +2.3 °C | 359 mm | -13 mm |
| Jul | 24.5 °C | +2.7 °C | 256 mm | -230 mm |
| Aug | 24.5 °C | +1.6 °C | 380 mm | +71 mm |
| Sep | 21.5 °C | +2.7 °C | 373 mm | +49 mm |
| Oct | 13.8 °C | +1.1 °C | 319 mm | +105 mm |
| Nov | 6.2 °C | +0.7 °C | 128 mm | -48 mm |
| Dec | -0.1 °C | +1.9 °C | 224 mm | +37 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 Ōmachi?
Ōmachi has a warm-summer humid continental climate (Köppen Dfb). Over 1940-2025, the average annual temperature is 5.2 °C and it receives 3,042 mm of precipitation per year.
What is the hottest day ever recorded in Ōmachi?
The hottest day measured in Ōmachi between 1940 and 2025 was 5 August 2018, reaching 28.5 °C.
What is the coldest day in Ōmachi?
The coldest day measured in Ōmachi between 1940 and 2025 was 14 February 1942, at -23.8 °C.
Does it snow in Ōmachi?
Yes. Ōmachi gets on average 524.0 cm of snow per year and has around 168 frost days.
Has the climate of Ōmachi warmed?
Yes: Ōmachi warmed by +2.7 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Ōmachi?
The wettest day measured in Ōmachi between 1940 and 2025 was 14 August 2021, with 202 mm of rain in 24 hours.
What was the windiest day in Ōmachi?
The windiest day measured in Ōmachi between 1940 and 2025 was 16 September 1961, with winds reaching 37.3 km/h.
What is the warmest month in Ōmachi?
The warmest month in Ōmachi is August (18.9 °C on average); the coldest is January (-8.4 °C).
How much does it rain in Ōmachi?
Ōmachi receives on average 3,042 mm of precipitation per year, spread over about 240 rainy days.
Is it sunny in Ōmachi?
Ōmachi gets on average 8.7 hours of sunshine per day, roughly 3,175 hours per year over 1940-2025.
What is the biggest single-day snowfall in Ōmachi?
The heaviest 24-hour snowfall measured in Ōmachi between 1940 and 2025 was 15 February 2014, with 36.7 cm.
Are there tropical nights in Ōmachi?
Almost never: tropical nights (temperature staying above 20 °C) are virtually non-existent in Ōmachi.
What was the most extreme apparent temperature in Ōmachi?
In Ōmachi, between 1940 and 2025, the highest apparent temperature reached 33.0 °C on 8 August 2019, and the lowest was -28.6 °C on 14 February 1942.
Compare Ōmachi with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Ōmachi