| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 4.8° | — | 43mm | 7.7 | 36 |
| February | 5.7° | — | 42.7mm | 7.6 | 39 |
| March | 9.6° | — | 108.8mm | 8.9 | 49 |
| April | 15° | — | 151.5mm | 10.3 | 63 |
| May | 20.1° | — | 143.7mm | 10.2 | 80 |
| June | 22.7° | — | 173.6mm | 11.4 | 77 |
| July | 26.2° | — | 192mm | 14.9 | 70 |
| August | 27.6° | — | 178.3mm | 13.2 | 71 |
| September | 24.5° | — | 183mm | 11.8 | 76 |
| October | 19.2° | — | 169.5mm | 9.8 | 78 |
| November | 13.5° | — | 85.2mm | 8.2 | 63 |
| December | 7.5° | — | 78.4mm | 9.2 | 42 |
January in Ōshū averages a daily high of 4.8°C. Expect roughly 7.7 wet days totalling 43mm. Demanding conditions — pack for it and plan indoor options.
February in Ōshū averages a daily high of 5.7°C. Expect roughly 7.6 wet days totalling 42.7mm. Demanding conditions — pack for it and plan indoor options.
March in Ōshū averages a daily high of 9.6°C. Expect roughly 8.9 wet days totalling 108.8mm. Demanding conditions — pack for it and plan indoor options.
April in Ōshū averages a daily high of 15°C. Expect roughly 10.3 wet days totalling 151.5mm. Generally workable, with some weather to plan around.
May in Ōshū averages a daily high of 20.1°C. Expect roughly 10.2 wet days totalling 143.7mm. Comfortable conditions for being outdoors all day.
June in Ōshū averages a daily high of 22.7°C. Expect roughly 11.4 wet days totalling 173.6mm. Comfortable conditions for being outdoors all day.
July in Ōshū averages a daily high of 26.2°C. Expect roughly 14.9 wet days totalling 192mm. Generally workable, with some weather to plan around.
August in Ōshū averages a daily high of 27.6°C. Expect roughly 13.2 wet days totalling 178.3mm. Generally workable, with some weather to plan around.
September in Ōshū averages a daily high of 24.5°C. Expect roughly 11.8 wet days totalling 183mm. Comfortable conditions for being outdoors all day.
October in Ōshū averages a daily high of 19.2°C. Expect roughly 9.8 wet days totalling 169.5mm. Comfortable conditions for being outdoors all day.
November in Ōshū averages a daily high of 13.5°C. Expect roughly 8.2 wet days totalling 85.2mm. Generally workable, with some weather to plan around.
December in Ōshū averages a daily high of 7.5°C. Expect roughly 9.2 wet days totalling 78.4mm. 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. Ōshū peaks at 80.
Based on 30 years of records, May–June scores highest for comfort in Ōshū, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 27.6°C.
July is the wettest, averaging 192mm of rain across roughly 14.9 wet days.
January is the coolest month, with average daily highs around 4.8°C.