Climate averages 1991–2020
Niiza weather
in September.
A warm, very wet month: the 3rd warmest and the 11th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Niiza: daytime highs average 26.0°C and nights cool to about 19.6°C. By daytime temperature it is the 3rd warmest of the 12 months.
Expect about 204 mm of rain on roughly 15 days, which makes September a very wet month (the 11th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 26 min on an average September day.
The nearest other city in this atlas is Tokorozawa (8 km away). In September its highs average 25.2°C, 0.8°C cooler than Niiza, with 204 mm of rain.
Among the 303 cities listed in Japan, Niiza ranks joint 159th of 303 for the warmest September highs and joint 209th of 303 for the driest September (rainfall, lowest first). The mean September high of those 303 cities is 25.7°C; Niiza is 0.3°C warmer than that mean.
From September to October, average highs fall by 5.5°C to 20.5°C, and monthly rainfall rises from 204 mm to 215 mm.
The annual picture
September 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
Niiza climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 7.9°C-1.6°C | -1.6°C | 69 | 7.5 | 10.010 h |
| February | 8.9°C-0.9°C | -0.9°C | 66 | 8.5 | 10.911 h |
| March | 12.4°C2.7°C | 2.7°C | 120 | 13.2 | 11.912 h |
| April | 17.5°C7.9°C | 7.9°C | 123 | 12.8 | 13.113 h |
| May | 22.0°C13.4°C | 13.4°C | 139 | 13.1 | 14.014 h |
| June | 24.8°C17.7°C | 17.7°C | 177 | 15.4 | 14.515 h |
| July | 28.5°C21.8°C | 21.8°C | 182 | 16.4 | 14.314 h |
| August | 29.9°C23.2°C | 23.2°C | 142 | 15.4 | 13.514 h |
| September, selected | 26.0°C19.6°C | 19.6°C | 204 | 14.9 | 12.412 h |
| October | 20.5°C13.5°C | 13.5°C | 215 | 13.7 | 11.311 h |
| November | 15.3°C7.2°C | 7.2°C | 92 | 10.2 | 10.310 h |
| December | 10.3°C1.4°C | 1.4°C | 61 | 7.4 | 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
September in nearby cities
- Tokorozawa in SeptemberJapan · 8 kmHigh 25.2°C · Low 18.9°C · 204 mm rain
- Yono in SeptemberJapan · 10 kmHigh 26.0°C · Low 19.4°C · 171 mm rain
- Kawagoe in SeptemberJapan · 12 kmHigh 25.6°C · Low 19.0°C · 186 mm rain
- Musashino in SeptemberJapan · 13 kmHigh 25.6°C · Low 19.7°C · 204 mm rain
- Saitama in SeptemberJapan · 13 kmHigh 26.3°C · Low 19.6°C · 171 mm rain
- Sayama in SeptemberJapan · 14 kmHigh 25.3°C · Low 18.8°C · 204 mm rain
- Kawaguchi in SeptemberJapan · 14 kmHigh 26.3°C · Low 19.9°C · 180 mm rain
- Iruma in SeptemberJapan · 17 kmHigh 25.0°C · Low 18.6°C · 249 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 Niiza) is explained once on the Niiza year overview and on the Sources, method and limits page.
Tokorozawa, Fuchū and Hino lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.