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Karatsu Weather by Month
Average temperatures, rainfall and humidity for Karatsu, Japan, month by month, built from OpenWeather's historical records. Use it to see what a typical Karatsu month looks like before you travel — then check the live Karatsu forecast for the days ahead.
Warmest month
August
33°C average high
Coolest month
January
3°C average low
Wettest month
June
182 mm of rain
Driest month
January
51 mm of rain
Average temperature and rainfall in Karatsu 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 | 10°C | 3°C | -5°C / 21°C | 51 mm | 67% | 10 km/h |
| February | 11°C | 4°C | -6°C / 22°C | 69 mm | 66% | 12 km/h |
| March | 16°C | 7°C | -2°C / 27°C | 80 mm | 65% | 11 km/h |
| April | 20°C | 12°C | 2°C / 30°C | 119 mm | 66% | 11 km/h |
| May | 25°C | 16°C | 7°C / 34°C | 97 mm | 66% | 10 km/h |
| June | 27°C | 21°C | 14°C / 37°C | 182 mm | 73% | 9 km/h |
| July | 32°C | 25°C | 12°C / 39°C | 147 mm | 72% | 10 km/h |
| August | 33°C | 25°C | 18°C / 42°C | 144 mm | 70% | 10 km/h |
| September | 29°C | 22°C | 13°C / 40°C | 138 mm | 72% | 10 km/h |
| October | 24°C | 16°C | 7°C / 35°C | 74 mm | 67% | 10 km/h |
| November | 19°C | 10°C | 1°C / 29°C | 60 mm | 66% | 10 km/h |
| December | 12°C | 4°C | -3°C / 23°C | 60 mm | 64% | 11 km/h |
Best time to visit Karatsu
The most comfortable time to visit Karatsu 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 1222 mm a year.
Travellers who prefer heat should aim for August, when highs average 33°C. June is the month to avoid if rain would spoil your plans — it averages 182 mm, roughly 4× the rainfall of January.
Source: OpenWeather historical and statistical weather data. Values are long-term averages, not a forecast — see the Karatsu forecast for what is happening now.