Average annual temperature is 12.7 °C
Absolute maximum temperature: 34.5 °C
Absolute minimum temperature: -10.2 °C
Number of sunny days: 74 days
Number of rainy days: 240 days
Number of snow days: 51 days
Look at detailed online map of Koiso
* Weather data for Koiso Japan is based on climate observations for 2026 year
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Absolute maximum temperature (°C) | 10.8 | 8.8 | 20.6 | 19.2 | 22.2 | 26.3 | 29.3 | 34.5 | 31.4 | 21.8 | 22.8 | 13.7 |
| Average daytime temperature (°C) | 1.2 | 2.2 | 9.3 | 12.9 | 17.3 | 22.4 | 25.6 | 31.3 | 26.0 | 17.8 | 11.8 | 4.5 |
| Average temperature (°C) | -0.7 | 0.5 | 6.2 | 9.9 | 14.1 | 19.9 | 23.6 | 28.4 | 22.9 | 14.9 | 9.1 | 2.4 |
| Average night temperature (°C) | -2.5 | -1.3 | 3.5 | 7.5 | 11.6 | 17.7 | 21.8 | 26.0 | 20.4 | 12.7 | 6.4 | 0.3 |
| Absolute minimum temperature (°C) | -10.2 | -6.3 | -1.9 | 1.9 | 4.9 | 12.7 | 17.3 | 23.8 | 13.9 | 6.2 | -1.7 | -5.5 |
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight maximum duration (h) | 10.0 | 11.0 | 12.0 | 13.0 | 14.0 | 15.0 | 15.0 | 14.0 | 13.0 | 11.0 | 10.0 | 9.0 |
| Daylight mean duration (h) | 9.7 | 10.7 | 11.9 | 13.3 | 14.4 | 15.0 | 14.7 | 13.7 | 12.5 | 11.1 | 10.0 | 9.3 |
| Daylight minimum duration (h) | 9.0 | 10.0 | 11.0 | 12.0 | 13.0 | 14.0 | 14.0 | 13.0 | 11.0 | 10.0 | 9.0 | 9.0 |
| Sunshine mean duration (h) | 5.3 | 5.8 | 8.0 | 8.7 | 9.7 | 8.5 | 9.3 | 12.0 | 7.7 | 7.7 | 5.1 | 3.6 |
| Precipitation (mm) | 155 | 140 | 116 | 230 | 200 | 162 | 412 | 91 | 190 | 222 | 334 | 185 |
| Sunny days | 0 | 2 | 12 | 6 | 13 | 10 | 5 | 10 | 8 | 6 | 2 | 0 |
| Rainy days | 10 | 12 | 17 | 24 | 18 | 20 | 26 | 21 | 22 | 25 | 25 | 20 |
| Snow days | 21 | 14 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 11 |
The best time to visit Koiso during the most sunny months:
The largest precipitation sum in Koiso is at