Sanmu climate — normals and trends
Sanmu (Japan) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 15.7 °C and it receives 1,432 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 (26.3 °C on average) and the coldest is January (5.5 °C). Rainfall peaks in October.
Sanmu averages 9 frost days, 23 hot days (≥ 30 °C) and 145 rainy days per year.
Sanmu has warmed by +1.8 °C between 1940 and 2025, or +0.21 °C per decade. This trend is statistically significant.
The number of frost days there went from about 18 to 0 per year over the period.
The hottest day of the period reached 36.0 °C (on 16 August 2007) and the coldest -7.5 °C (on 5 February 1952).
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
SanmuChiba
- coords
- 35.63°, 140.42°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
15.7°C
Average daily high
18.7°C
Average daily low
13.0°C
Annual rainfall
1,432mm
Sunshine / day
8.4h
Mean relative humidity
74%
Average peak wind
20.7km/h
Seasonal range
20.8°C
Frost days (< 0 °C)
9 d/yr
Hot days (≥ 30 °C)
23 d/yr
Rainy days (≥ 1 mm)
145 d/yr
Annual snowfall
5.8 cm
Average feels-like high
18.2 °C
Average feels-like low
11.7 °C
Average peak gust
37.6 km/h
Tropical nights (≥ 20 °C)
89 d/yr
Solar radiation
14.4 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.8 °C
since 1940
+0.2 °C per decade · r² = 0.57 · 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
36.0 °C
16 August 2007
Coldest day
-7.5 °C
5 February 1952
Wettest day
176 mm
26 September 1958
Windiest day
75.5 km/h
5 December 2004
Strongest gust
147.6 km/h
1 October 2018
Hottest feels-like
43.5 °C
16 August 2007
Coldest feels-like
-13.1 °C
5 February 1952
Snowiest day
14.8 cm
15 February 1951
Sunniest day
14.0 h
23 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 | 10.7 °C | +1.8 °C | 50 mm | -16 mm |
| Feb | 10.2 °C | +0.8 °C | 16 mm | -60 mm |
| Mar | 14.6 °C | +2.2 °C | 153 mm | +37 mm |
| Apr | 18.5 °C | +1.3 °C | 125 mm | +11 mm |
| May | 21.4 °C | +0.2 °C | 187 mm | +59 mm |
| Jun | 26.7 °C | +2.8 °C | 122 mm | -35 mm |
| Jul | 30.3 °C | +2.8 °C | 72 mm | -61 mm |
| Aug | 31.7 °C | +2.5 °C | 61 mm | -50 mm |
| Sep | 29.0 °C | +3.1 °C | 129 mm | -34 mm |
| Oct | 21.6 °C | +0.7 °C | 151 mm | -41 mm |
| Nov | 16.5 °C | +0.2 °C | 65 mm | -42 mm |
| Dec | 12.6 °C | +1.1 °C | 86 mm | +16 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 Sanmu?
Sanmu has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 15.7 °C and it receives 1,432 mm of precipitation per year.
What is the hottest day ever recorded in Sanmu?
The hottest day measured in Sanmu between 1940 and 2025 was 16 August 2007, reaching 36.0 °C.
What is the coldest day in Sanmu?
The coldest day measured in Sanmu between 1940 and 2025 was 5 February 1952, at -7.5 °C.
Does it snow in Sanmu?
Yes. Sanmu gets on average 5.8 cm of snow per year and has around 9 frost days.
Has the climate of Sanmu warmed?
Yes: Sanmu warmed by +1.8 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Sanmu?
The wettest day measured in Sanmu between 1940 and 2025 was 26 September 1958, with 176 mm of rain in 24 hours.
What was the windiest day in Sanmu?
The windiest day measured in Sanmu between 1940 and 2025 was 5 December 2004, with winds reaching 75.5 km/h.
What is the warmest month in Sanmu?
The warmest month in Sanmu is August (26.3 °C on average); the coldest is January (5.5 °C).
How much does it rain in Sanmu?
Sanmu receives on average 1,432 mm of precipitation per year, spread over about 145 rainy days.
Is it sunny in Sanmu?
Sanmu gets on average 8.4 hours of sunshine per day, roughly 3,066 hours per year over 1940-2025.
What is the biggest single-day snowfall in Sanmu?
The heaviest 24-hour snowfall measured in Sanmu between 1940 and 2025 was 15 February 1951, with 14.8 cm.
Are there tropical nights in Sanmu?
Yes: Sanmu has on average 89 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Sanmu?
In Sanmu, between 1940 and 2025, the highest apparent temperature reached 43.5 °C on 16 August 2007, and the lowest was -13.1 °C on 5 February 1952.
Compare Sanmu with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Sanmu