Click on a day for an hourly weather forecast
The temperatures in Nagano in September are comfortable with low of 14°C and and high up to 25°C.
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 | 2° / -6° | 21 | 1 | 19 | 85 mm | Awful | Nagano in January |
| February | 4° / -6° | 18 | 2 | 13 | 62 mm | Awful | Nagano in February |
| March | 9° / -2° | 14 | 10 | 8 | 60 mm | Awful | Nagano in March |
| April | 15° / 3° | 10 | 19 | 1 | 54 mm | Ok | Nagano in April |
| May | 21° / 9° | 9 | 23 | 0 | 51 mm | Ok | Nagano in May |
| June | 25° / 13° | 11 | 20 | 0 | 63 mm | Good | Nagano in June |
| July | 28° / 18° | 16 | 15 | 0 | 112 mm | Good | Nagano in July |
| August | 29° / 18° | 15 | 16 | 0 | 83 mm | Ok | Nagano in August |
| September | 25° / 14° | 12 | 18 | 0 | 83 mm | Good | Nagano in September |
| October | 19° / 8° | 11 | 21 | 0 | 73 mm | Ok | Nagano in October |
| November | 13° / 3° | 12 | 17 | 1 | 60 mm | Bad | Nagano in November |
| December | 5° / -2° | 18 | 4 | 13 | 85 mm | Awful | Nagano in December |