| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 3.7° | — | 45.8mm | 11.2 | 25 |
| February | 5.5° | — | 48.6mm | 10.9 | 32 |
| March | 10.2° | — | 56.9mm | 10.2 | 48 |
| April | 17.5° | — | 67.6mm | 10.5 | 71 |
| May | 23.4° | — | 79.7mm | 9.3 | 81 |
| June | 26.2° | — | 108.3mm | 11.6 | 77 |
| July | 29.9° | — | 138.1mm | 14.6 | 59 |
| August | 31.3° | — | 119.1mm | 11.1 | 61 |
| September | 26.2° | — | 122.9mm | 10.1 | 80 |
| October | 19.7° | — | 113.8mm | 8.7 | 82 |
| November | 13.4° | — | 50mm | 8.8 | 61 |
| December | 7.2° | — | 53.3mm | 11.1 | 37 |
January in Nagano averages a daily high of 3.7°C. Expect roughly 11.2 wet days totalling 45.8mm. A hard month to visit for comfort alone.
February in Nagano averages a daily high of 5.5°C. Expect roughly 10.9 wet days totalling 48.6mm. A hard month to visit for comfort alone.
March in Nagano averages a daily high of 10.2°C. Expect roughly 10.2 wet days totalling 56.9mm. Demanding conditions — pack for it and plan indoor options.
April in Nagano averages a daily high of 17.5°C. Expect roughly 10.5 wet days totalling 67.6mm. Generally workable, with some weather to plan around.
May in Nagano averages a daily high of 23.4°C. Expect roughly 9.3 wet days totalling 79.7mm. Comfortable conditions for being outdoors all day.
June in Nagano averages a daily high of 26.2°C. Expect roughly 11.6 wet days totalling 108.3mm. Comfortable conditions for being outdoors all day.
July in Nagano averages a daily high of 29.9°C. Expect roughly 14.6 wet days totalling 138.1mm. Generally workable, with some weather to plan around.
August in Nagano averages a daily high of 31.3°C. Expect roughly 11.1 wet days totalling 119.1mm. Generally workable, with some weather to plan around.
September in Nagano averages a daily high of 26.2°C. Expect roughly 10.1 wet days totalling 122.9mm. Comfortable conditions for being outdoors all day.
October in Nagano averages a daily high of 19.7°C. Expect roughly 8.7 wet days totalling 113.8mm. Comfortable conditions for being outdoors all day.
November in Nagano averages a daily high of 13.4°C. Expect roughly 8.8 wet days totalling 50mm. Generally workable, with some weather to plan around.
December in Nagano averages a daily high of 7.2°C. Expect roughly 11.1 wet days totalling 53.3mm. Demanding conditions — pack for it and plan indoor options.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Nagano peaks at 82.
Based on 30 years of records, May–June scores highest for comfort in Nagano, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 31.3°C.
July is the wettest, averaging 138.1mm of rain across roughly 14.6 wet days.
January is the coolest month, with average daily highs around 3.7°C.