| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 10.4° | — | 50.2mm | 5.2 | 59 |
| February | 11.7° | — | 89.1mm | 7.1 | 59 |
| March | 15.4° | — | 166.9mm | 9.3 | 67 |
| April | 20° | — | 193mm | 10.3 | 79 |
| May | 24° | — | 215.6mm | 10.1 | 80 |
| June | 26.7° | — | 218.8mm | 13.1 | 74 |
| July | 30.4° | — | 237.6mm | 11.6 | 63 |
| August | 32° | — | 151.5mm | 9.9 | 60 |
| September | 28.9° | — | 246.4mm | 12.2 | 68 |
| October | 24° | — | 234.1mm | 10.1 | 80 |
| November | 18.6° | — | 126.5mm | 8.1 | 79 |
| December | 12.8° | — | 68.7mm | 5.3 | 66 |
January in Kosai averages a daily high of 10.4°C. Expect roughly 5.2 wet days totalling 50.2mm. Generally workable, with some weather to plan around.
February in Kosai averages a daily high of 11.7°C. Expect roughly 7.1 wet days totalling 89.1mm. Generally workable, with some weather to plan around.
March in Kosai averages a daily high of 15.4°C. Expect roughly 9.3 wet days totalling 166.9mm. Generally workable, with some weather to plan around.
April in Kosai averages a daily high of 20°C. Expect roughly 10.3 wet days totalling 193mm. Comfortable conditions for being outdoors all day.
May in Kosai averages a daily high of 24°C. Expect roughly 10.1 wet days totalling 215.6mm. Comfortable conditions for being outdoors all day.
June in Kosai averages a daily high of 26.7°C. Expect roughly 13.1 wet days totalling 218.8mm. Generally workable, with some weather to plan around.
July in Kosai averages a daily high of 30.4°C. Expect roughly 11.6 wet days totalling 237.6mm. Generally workable, with some weather to plan around.
August in Kosai averages a daily high of 32°C. Expect roughly 9.9 wet days totalling 151.5mm. Generally workable, with some weather to plan around.
September in Kosai averages a daily high of 28.9°C. Expect roughly 12.2 wet days totalling 246.4mm. Generally workable, with some weather to plan around.
October in Kosai averages a daily high of 24°C. Expect roughly 10.1 wet days totalling 234.1mm. Comfortable conditions for being outdoors all day.
November in Kosai averages a daily high of 18.6°C. Expect roughly 8.1 wet days totalling 126.5mm. Comfortable conditions for being outdoors all day.
December in Kosai averages a daily high of 12.8°C. Expect roughly 5.3 wet days totalling 68.7mm. 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. Kosai peaks at 80.
Based on 30 years of records, April–June scores highest for comfort in Kosai, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 32°C.
September is the wettest, averaging 246.4mm of rain across roughly 12.2 wet days.
January is the coolest month, with average daily highs around 10.4°C.