Iwakuni climate — normals and trends
Iwakuni (Japan) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 15.0 °C and it receives 1,603 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 (26.5 °C on average) and the coldest is January (4.2 °C). Rainfall peaks in June.
Iwakuni averages 23 frost days, 27 hot days (≥ 30 °C) and 126 rainy days per year.
Iwakuni has warmed by +2.5 °C between 1940 and 2025, or +0.30 °C per decade. This trend is statistically significant.
The number of frost days there went from about 42 to 4 per year over the period.
The hottest day of the period reached 35.6 °C (on 16 August 1983) and the coldest -8.2 °C (on 16 February 1977).
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
IwakuniYamaguchi
- coords
- 34.16°, 132.22°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
15.0°C
Average daily high
18.6°C
Average daily low
11.8°C
Annual rainfall
1,603mm
Sunshine / day
8.8h
Mean relative humidity
75%
Average peak wind
14.2km/h
Seasonal range
22.3°C
Frost days (< 0 °C)
23 d/yr
Hot days (≥ 30 °C)
27 d/yr
Rainy days (≥ 1 mm)
126 d/yr
Annual snowfall
10.6 cm
Average feels-like high
18.6 °C
Average feels-like low
11.0 °C
Average peak gust
35.1 km/h
Tropical nights (≥ 20 °C)
85 d/yr
Solar radiation
14.7 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+2.5 °C
since 1940
+0.3 °C per decade · r² = 0.73 · 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
35.6 °C
16 August 1983
Coldest day
-8.2 °C
16 February 1977
Wettest day
183 mm
6 September 2005
Windiest day
73.6 km/h
7 September 2004
Strongest gust
193.0 km/h
7 September 2004
Hottest feels-like
42.3 °C
16 August 2024
Coldest feels-like
-14.5 °C
16 February 1977
Snowiest day
22.8 cm
15 February 1968
Sunniest day
13.9 h
4 June 2025
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 | 8.2 °C | +0.5 °C | 15 mm | -32 mm |
| Feb | 6.7 °C | -1.8 °C | 51 mm | -17 mm |
| Mar | 13.4 °C | +1.2 °C | 165 mm | +57 mm |
| Apr | 18.3 °C | +0.9 °C | 92 mm | -52 mm |
| May | 21.5 °C | -0.1 °C | 238 mm | +79 mm |
| Jun | 26.4 °C | +1.9 °C | 313 mm | +71 mm |
| Jul | 31.5 °C | +3.1 °C | 92 mm | -144 mm |
| Aug | 31.2 °C | +1.5 °C | 188 mm | +19 mm |
| Sep | 28.4 °C | +2.1 °C | 292 mm | +90 mm |
| Oct | 23.0 °C | +1.8 °C | 98 mm | -9 mm |
| Nov | 16.6 °C | +0.8 °C | 30 mm | -43 mm |
| Dec | 11.2 °C | +0.9 °C | 44 mm | -4 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 Iwakuni?
Iwakuni has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 15.0 °C and it receives 1,603 mm of precipitation per year.
What is the hottest day ever recorded in Iwakuni?
The hottest day measured in Iwakuni between 1940 and 2025 was 16 August 1983, reaching 35.6 °C.
What is the coldest day in Iwakuni?
The coldest day measured in Iwakuni between 1940 and 2025 was 16 February 1977, at -8.2 °C.
Does it snow in Iwakuni?
Yes. Iwakuni gets on average 10.6 cm of snow per year and has around 23 frost days.
Has the climate of Iwakuni warmed?
Yes: Iwakuni warmed by +2.5 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Iwakuni?
The wettest day measured in Iwakuni between 1940 and 2025 was 6 September 2005, with 183 mm of rain in 24 hours.
What was the windiest day in Iwakuni?
The windiest day measured in Iwakuni between 1940 and 2025 was 7 September 2004, with winds reaching 73.6 km/h.
What is the warmest month in Iwakuni?
The warmest month in Iwakuni is August (26.5 °C on average); the coldest is January (4.2 °C).
How much does it rain in Iwakuni?
Iwakuni receives on average 1,603 mm of precipitation per year, spread over about 126 rainy days.
Is it sunny in Iwakuni?
Iwakuni 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 Iwakuni?
The heaviest 24-hour snowfall measured in Iwakuni between 1940 and 2025 was 15 February 1968, with 22.8 cm.
Are there tropical nights in Iwakuni?
Yes: Iwakuni has on average 85 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Iwakuni?
In Iwakuni, between 1940 and 2025, the highest apparent temperature reached 42.3 °C on 16 August 2024, and the lowest was -14.5 °C on 16 February 1977.
Compare Iwakuni with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Iwakuni