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Isahaya Weather by Month
Average temperatures, rainfall and humidity for Isahaya, Japan, month by month, built from OpenWeather’s historical records. Use it to see what a typical Isahaya month looks like before you travel — then check the live Isahaya forecast for the days ahead.
Warmest month
August
32°C average high
Coolest month
January
4°C average low
Wettest month
June
159 mm of rain
Driest month
January
41 mm of rain
Average temperature and rainfall in Isahaya by month
Averages of the daily highs and lows recorded in each month, with total rainfall, mean humidity and mean wind speed.
| Month | Avg high | Avg low | Record low / high | Rainfall | Humidity | Wind |
|---|---|---|---|---|---|---|
| January | 11°C | 4°C | -7°C / 20°C | 41 mm | 73% | 16 km/h |
| February | 12°C | 5°C | -5°C / 20°C | 73 mm | 73% | 16 km/h |
| March | 16°C | 8°C | 0°C / 24°C | 88 mm | 72% | 14 km/h |
| April | 20°C | 12°C | 3°C / 27°C | 120 mm | 72% | 14 km/h |
| May | 24°C | 17°C | 8°C / 32°C | 84 mm | 75% | 12 km/h |
| June | 26°C | 21°C | 14°C / 32°C | 159 mm | 82% | 12 km/h |
| July | 31°C | 25°C | 19°C / 37°C | 140 mm | 81% | 12 km/h |
| August | 32°C | 26°C | 20°C / 38°C | 121 mm | 78% | 13 km/h |
| September | 29°C | 22°C | 12°C / 37°C | 120 mm | 78% | 13 km/h |
| October | 24°C | 17°C | 7°C / 32°C | 65 mm | 74% | 14 km/h |
| November | 19°C | 11°C | 0°C / 25°C | 66 mm | 73% | 14 km/h |
| December | 13°C | 5°C | -4°C / 23°C | 46 mm | 72% | 16 km/h |
Best time to visit Isahaya
The most comfortable time to visit Isahaya is generally May and October to November, balancing mild daytime temperatures against the driest stretch of the year. The city has strongly marked seasons and rain concentrates around June, totalling about 1,122 mm a year.
Travellers who prefer heat should aim for August, when highs average 32°C. June is the month to avoid if rain would spoil your plans — it averages 159 mm, roughly 4× the rainfall of the driest month (January).
Source: OpenWeather historical and statistical weather data. Values are long-term averages, not a forecast — see the Isahaya forecast for what is happening now.