Iruma, Japan climate
Cfa Humid subtropical
Iruma has a seasonal mild-temperate climate (Humid subtropical, Köppen Cfa). The hottest month is August with an average daily high near 31°C, while the coldest is January averaging around −2°C at night. Precipitation totals about 1563 mm a year and is strongly seasonal — September alone averages 234 mm while December barely receives 45 mm.
Temperature & precipitation
Daily high–low temperature range with the monthly average, plus monthly precipitation · 1991–2020 normals · hover a month for the exact figuresHours of sunshine per day
Estimated sunny hours each month — daylight length × clear-sky fraction · 1991–2020 monthly cloud cover (NASA POWER)Iruma climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 9 | 10 | 13 | 19 | 23 | 26 | 30 | 31 | 27 | 21 | 16 | 12 |
| Avg temp (°C) | 3 | 4 | 8 | 13 | 18 | 21 | 25 | 26 | 22 | 17 | 11 | 6 |
| Avg low (°C) | −2 | −1 | 2 | 7 | 13 | 17 | 21 | 22 | 18 | 12 | 6 | 0 |
| Precipitation (mm) | 50 | 45 | 90 | 108 | 124 | 176 | 198 | 213 | 234 | 209 | 71 | 45 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°C) | 9 | 10 | 13 | 19 | 23 | 26 |
| Avg temp (°C) | 3 | 4 | 8 | 13 | 18 | 21 |
| Avg low (°C) | −2 | −1 | 2 | 7 | 13 | 17 |
| Precipitation (mm) | 50 | 45 | 90 | 108 | 124 | 176 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°C) | 30 | 31 | 27 | 21 | 16 | 12 |
| Avg temp (°C) | 25 | 26 | 22 | 17 | 11 | 6 |
| Avg low (°C) | 21 | 22 | 18 | 12 | 6 | 0 |
| Precipitation (mm) | 198 | 213 | 234 | 209 | 71 | 45 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 46 | 52 | 60 | 64 | 70 | 82 | 75 | 64 | 71 | 67 | 56 | 45 |
| Relative humidity (%) | 76 | 75 | 74 | 74 | 76 | 80 | 81 | 81 | 83 | 82 | 80 | 78 |
| Wind speed (m/s) | 2.1 | 2.3 | 2.3 | 2.4 | 2.1 | 1.9 | 1.9 | 1.8 | 1.9 | 1.8 | 1.7 | 1.8 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 46 | 52 | 60 | 64 | 70 | 82 |
| Relative humidity (%) | 76 | 75 | 74 | 74 | 76 | 80 |
| Wind speed (m/s) | 2.1 | 2.3 | 2.3 | 2.4 | 2.1 | 1.9 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 75 | 64 | 71 | 67 | 56 | 45 |
| Relative humidity (%) | 81 | 81 | 83 | 82 | 80 | 78 |
| Wind speed (m/s) | 1.9 | 1.8 | 1.9 | 1.8 | 1.7 | 1.8 |
Methodology & sources
Temperature & precipitation — the official 1991–2020 climate normals from the Japan Meteorological Agency, measured at Ome, about 6 km from the city centre.
Cloud, humidity, wind & sunshine — modelled estimates from NASA POWER, NASA's satellite-and-reanalysis climatology. This is the standard global source for atmospheric variables, which are not measured at most weather stations.