| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 11.2° | — | 66.8mm | 9.5 | 53 |
| February | 12.6° | — | 125.9mm | 11.5 | 53 |
| March | 15.9° | — | 138.6mm | 10.9 | 65 |
| April | 20° | — | 160.6mm | 10.6 | 79 |
| May | 23.7° | — | 226.2mm | 10.6 | 79 |
| June | 26.2° | — | 475.7mm | 16.5 | 70 |
| July | 30.1° | — | 361.9mm | 12.6 | 62 |
| August | 31.3° | — | 259.4mm | 12.6 | 58 |
| September | 28.8° | — | 254.3mm | 11.3 | 70 |
| October | 24.3° | — | 94mm | 7.4 | 85 |
| November | 18.9° | — | 111.8mm | 10.6 | 75 |
| December | 13.3° | — | 101.1mm | 11.5 | 56 |
January in Izumi averages a daily high of 11.2°C. Expect roughly 9.5 wet days totalling 66.8mm. Demanding conditions — pack for it and plan indoor options.
February in Izumi averages a daily high of 12.6°C. Expect roughly 11.5 wet days totalling 125.9mm. Demanding conditions — pack for it and plan indoor options.
March in Izumi averages a daily high of 15.9°C. Expect roughly 10.9 wet days totalling 138.6mm. Generally workable, with some weather to plan around.
April in Izumi averages a daily high of 20°C. Expect roughly 10.6 wet days totalling 160.6mm. Comfortable conditions for being outdoors all day.
May in Izumi averages a daily high of 23.7°C. Expect roughly 10.6 wet days totalling 226.2mm. Comfortable conditions for being outdoors all day.
June in Izumi averages a daily high of 26.2°C. Expect roughly 16.5 wet days totalling 475.7mm. Generally workable, with some weather to plan around.
July in Izumi averages a daily high of 30.1°C. Expect roughly 12.6 wet days totalling 361.9mm. Generally workable, with some weather to plan around.
August in Izumi averages a daily high of 31.3°C. Expect roughly 12.6 wet days totalling 259.4mm. Generally workable, with some weather to plan around.
September in Izumi averages a daily high of 28.8°C. Expect roughly 11.3 wet days totalling 254.3mm. Generally workable, with some weather to plan around.
October in Izumi averages a daily high of 24.3°C. Expect roughly 7.4 wet days totalling 94mm. Comfortable conditions for being outdoors all day.
November in Izumi averages a daily high of 18.9°C. Expect roughly 10.6 wet days totalling 111.8mm. Comfortable conditions for being outdoors all day.
December in Izumi averages a daily high of 13.3°C. Expect roughly 11.5 wet days totalling 101.1mm. Generally workable, with some weather to plan around.
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. Izumi peaks at 85.
Based on 30 years of records, April–May scores highest for comfort in Izumi, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 31.3°C.
June is the wettest, averaging 475.7mm of rain across roughly 16.5 wet days.
January is the coolest month, with average daily highs around 11.2°C.