Click on a day for an hourly weather forecast
The temperatures in Nagano in September are quite cold with temperatures between 9°C and 23°C, warm clothes are a must.
You can expect rain for roughly half of the month of September in Nagano. We’re expecting roughly 8 to 15 days of rain, so your rubber boots and umbrella are going to see plenty of use this month if you’re keen on staying dry.
Our weather forecast can give you a great sense of what weather to expect in Nagano in September 2025.
If you’re planning to visit Nagano in the near future, we highly recommend that you review the 14 day weather forecast for Nagano before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -1° / -12° | 11 | 1 | 23 | 159 mm | Awful | Nagano in January |
| February | 1° / -11° | 9 | 3 | 18 | 145 mm | Awful | Nagano in February |
| March | 7° / -6° | 10 | 10 | 11 | 185 mm | Awful | Nagano in March |
| April | 15° / 1° | 9 | 20 | 2 | 172 mm | Bad | Nagano in April |
| May | 22° / 8° | 8 | 23 | 0 | 188 mm | Ok | Nagano in May |
| June | 24° / 10° | 12 | 18 | 0 | 280 mm | Good | Nagano in June |
| July | 27° / 13° | 17 | 14 | 0 | 393 mm | Good | Nagano in July |
| August | 28° / 14° | 13 | 18 | 0 | 292 mm | Good | Nagano in August |
| September | 23° / 9° | 10 | 20 | 0 | 216 mm | Good | Nagano in September |
| October | 18° / 3° | 6 | 25 | 0 | 203 mm | Good | Nagano in October |
| November | 10° / -2° | 6 | 22 | 1 | 142 mm | Ok | Nagano in November |
| December | 3° / -7° | 10 | 7 | 16 | 170 mm | Awful | Nagano in December |