Climate averages 1991–2020
Iruma weather
in April.
A mild, wet month: the 7th warmest and the 6th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
April is a mild month in Iruma: daytime highs average 16.8°C and nights cool to about 6.8°C. By daytime temperature it is the 7th warmest of the 12 months.
Expect about 146 mm of rain on roughly 15 days, which makes April a wet month (the 6th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 13 h 04 min on an average April day.
The nearest other city in this atlas is Sayama (6 km away). In April its highs average 17.2°C, about as warm as Iruma, with 123 mm of rain.
Among the 303 cities listed in Japan, Iruma ranks joint 201st of 303 for the warmest April highs and joint 230th of 303 for the driest April (rainfall, lowest first). The mean April high of those 303 cities is 16.7°C; Iruma is 0.1°C warmer than that mean.
From April to May, average highs rise by 4.4°C to 21.2°C, and monthly rainfall rises from 146 mm to 166 mm.
The annual picture
April in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Iruma climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 7.2°C-2.7°C | -2.7°C | 77 | 8.5 | 10.010 h |
| February | 8.1°C-2.0°C | -2.0°C | 76 | 9.7 | 10.911 h |
| March | 11.7°C1.5°C | 1.5°C | 139 | 15.2 | 11.912 h |
| April, selected | 16.8°C6.8°C | 6.8°C | 146 | 14.6 | 13.113 h |
| May | 21.2°C12.3°C | 12.3°C | 166 | 15.6 | 14.014 h |
| June | 23.8°C16.7°C | 16.7°C | 222 | 19.5 | 14.515 h |
| July | 27.5°C20.9°C | 20.9°C | 243 | 21.8 | 14.314 h |
| August | 28.7°C22.2°C | 22.2°C | 205 | 21.0 | 13.514 h |
| September | 25.0°C18.6°C | 18.6°C | 249 | 18.2 | 12.412 h |
| October | 19.6°C12.6°C | 12.6°C | 242 | 16.2 | 11.311 h |
| November | 14.6°C6.3°C | 6.3°C | 101 | 11.3 | 10.310 h |
| December | 9.7°C0.4°C | 0.4°C | 68 | 8.3 | 9.810 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
April in nearby cities
- Sayama in AprilJapan · 6 kmHigh 17.2°C · Low 6.8°C · 123 mm rain
- Hannō in AprilJapan · 6 kmHigh 17.4°C · Low 7.3°C · 146 mm rain
- Tokorozawa in AprilJapan · 9 kmHigh 16.9°C · Low 7.1°C · 123 mm rain
- Ōme in AprilJapan · 12 kmHigh 17.3°C · Low 7.3°C · 146 mm rain
- Kawagoe in AprilJapan · 15 kmHigh 17.4°C · Low 7.2°C · 106 mm rain
- Sakado in AprilJapan · 16 kmHigh 17.6°C · Low 7.3°C · 106 mm rain
- Akiruno in AprilJapan · 16 kmHigh 17.3°C · Low 7.5°C · 146 mm rain
- Hino in AprilJapan · 16 kmHigh 16.9°C · Low 7.3°C · 123 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Iruma) is explained once on the Iruma year overview and on the Sources, method and limits page.
Hachiōji, Ōme and Akiruno lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.