| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 3.8° | — | 30.4mm | 5.8 | 37 |
| February | 5.1° | — | 61.4mm | 6.5 | 39 |
| March | 10.1° | — | 94.2mm | 8.8 | 51 |
| April | 16.3° | — | 104.1mm | 10.7 | 67 |
| May | 21.7° | — | 111.9mm | 10.1 | 80 |
| June | 24.8° | — | 162.2mm | 13.4 | 73 |
| July | 28.4° | — | 213.5mm | 16.3 | 64 |
| August | 29.6° | — | 163.6mm | 13.3 | 63 |
| September | 24.7° | — | 194.6mm | 11.5 | 77 |
| October | 18.6° | — | 131.5mm | 8.8 | 78 |
| November | 12.7° | — | 63.9mm | 7.3 | 62 |
| December | 6.6° | — | 44.5mm | 5.8 | 46 |
January in Shiojiri averages a daily high of 3.8°C. Expect roughly 5.8 wet days totalling 30.4mm. Demanding conditions — pack for it and plan indoor options.
February in Shiojiri averages a daily high of 5.1°C. Expect roughly 6.5 wet days totalling 61.4mm. Demanding conditions — pack for it and plan indoor options.
March in Shiojiri averages a daily high of 10.1°C. Expect roughly 8.8 wet days totalling 94.2mm. Demanding conditions — pack for it and plan indoor options.
April in Shiojiri averages a daily high of 16.3°C. Expect roughly 10.7 wet days totalling 104.1mm. Generally workable, with some weather to plan around.
May in Shiojiri averages a daily high of 21.7°C. Expect roughly 10.1 wet days totalling 111.9mm. Comfortable conditions for being outdoors all day.
June in Shiojiri averages a daily high of 24.8°C. Expect roughly 13.4 wet days totalling 162.2mm. Generally workable, with some weather to plan around.
July in Shiojiri averages a daily high of 28.4°C. Expect roughly 16.3 wet days totalling 213.5mm. Generally workable, with some weather to plan around.
August in Shiojiri averages a daily high of 29.6°C. Expect roughly 13.3 wet days totalling 163.6mm. Generally workable, with some weather to plan around.
September in Shiojiri averages a daily high of 24.7°C. Expect roughly 11.5 wet days totalling 194.6mm. Comfortable conditions for being outdoors all day.
October in Shiojiri averages a daily high of 18.6°C. Expect roughly 8.8 wet days totalling 131.5mm. Comfortable conditions for being outdoors all day.
November in Shiojiri averages a daily high of 12.7°C. Expect roughly 7.3 wet days totalling 63.9mm. Generally workable, with some weather to plan around.
December in Shiojiri averages a daily high of 6.6°C. Expect roughly 5.8 wet days totalling 44.5mm. 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. Shiojiri peaks at 80.
Based on 30 years of records, May–June scores highest for comfort in Shiojiri, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 29.6°C.
July is the wettest, averaging 213.5mm of rain across roughly 16.3 wet days.
January is the coolest month, with average daily highs around 3.8°C.