| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 6.1° | — | 440.7mm | 25.2 | 26 |
| February | 6.9° | — | 245mm | 20.6 | 28 |
| March | 11.3° | — | 175.2mm | 18.3 | 42 |
| April | 17.7° | — | 112.2mm | 14.1 | 64 |
| May | 23° | — | 96.6mm | 10.8 | 78 |
| June | 26.1° | — | 128.5mm | 12.6 | 75 |
| July | 29.8° | — | 226.6mm | 15.5 | 59 |
| August | 31.4° | — | 186.5mm | 12.1 | 58 |
| September | 27.2° | — | 207.1mm | 14.9 | 69 |
| October | 21.4° | — | 239.3mm | 14.9 | 70 |
| November | 15.6° | — | 300.7mm | 18.9 | 56 |
| December | 9.7° | — | 498.5mm | 23.7 | 37 |
January in Jōetsu averages a daily high of 6.1°C. Expect roughly 25.2 wet days totalling 440.7mm. A hard month to visit for comfort alone.
February in Jōetsu averages a daily high of 6.9°C. Expect roughly 20.6 wet days totalling 245mm. A hard month to visit for comfort alone.
March in Jōetsu averages a daily high of 11.3°C. Expect roughly 18.3 wet days totalling 175.2mm. Demanding conditions — pack for it and plan indoor options.
April in Jōetsu averages a daily high of 17.7°C. Expect roughly 14.1 wet days totalling 112.2mm. Generally workable, with some weather to plan around.
May in Jōetsu averages a daily high of 23°C. Expect roughly 10.8 wet days totalling 96.6mm. Comfortable conditions for being outdoors all day.
June in Jōetsu averages a daily high of 26.1°C. Expect roughly 12.6 wet days totalling 128.5mm. Comfortable conditions for being outdoors all day.
July in Jōetsu averages a daily high of 29.8°C. Expect roughly 15.5 wet days totalling 226.6mm. Generally workable, with some weather to plan around.
August in Jōetsu averages a daily high of 31.4°C. Expect roughly 12.1 wet days totalling 186.5mm. Generally workable, with some weather to plan around.
September in Jōetsu averages a daily high of 27.2°C. Expect roughly 14.9 wet days totalling 207.1mm. Generally workable, with some weather to plan around.
October in Jōetsu averages a daily high of 21.4°C. Expect roughly 14.9 wet days totalling 239.3mm. Generally workable, with some weather to plan around.
November in Jōetsu averages a daily high of 15.6°C. Expect roughly 18.9 wet days totalling 300.7mm. Generally workable, with some weather to plan around.
December in Jōetsu averages a daily high of 9.7°C. Expect roughly 23.7 wet days totalling 498.5mm. 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. Jōetsu peaks at 78.
Based on 30 years of records, May–June scores highest for comfort in Jōetsu, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 31.4°C.
December is the wettest, averaging 498.5mm of rain across roughly 23.7 wet days.
January is the coolest month, with average daily highs around 6.1°C.