Climate Insights for Karatsu

The climate in Karatsu is temperate. The average annual temperature is 17°C and approximately 1786mm of precipitation falls per year. Karatsu receives a notable amount of rainfall throughout the year, including during its driest month. Karatsu is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: August, July, September. The coldest months are January, February, December, when temperatures can drop to 6°C. Light snow can occur between January and February.

Temperatures in Karatsu vary considerably across the year, with a 24°C difference between the coldest and warmest months. The warmest month is August, when average highs reach 30°C and the mean temperature sits around 28°C. January is the coolest month, with minimum temperatures around 6°C and an average of 8°C. Daily temperature variation is modest, with an average difference of 4°C between highs and lows. The sharpest temperature change occurs between November and December, with a 6°C shift in average temperatures.

Karatsu is a fairly wet location, receiving approximately 1786mm of precipitation annually, which averages out to around 149mm per month. The wettest month is July, averaging 261mm of rainfall. June and August also tend to see above-average precipitation. The driest month is December, with just 78mm. That's 183mm less than July, the wettest month. Precipitation varies noticeably between seasons, with the second half (July to December) of the year generally seeing more rainfall. Light snowfall can occur between January and February, totalling around 6cm annually. January is the snowiest month with approximately 3cm.

Karatsu is mildly breezy, with an average annual wind speed of 20km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is January, averaging 23km/h, noticeable enough to affect lighter outdoor activities. The calmest conditions occur in June, with average winds dropping to 17km/h, making it an ideal period for wind-sensitive activities. Wind conditions are fairly consistent throughout the year, varying by only 6km/h between the calmest and windiest months. Wind tends to be stronger during winter months, driven by seasonal pressure systems. The seasonal averages break down to 22km/h in winter, 19km/h in spring, 17km/h in summer, 20km/h in autumn.

It is currently spring in Karatsu, which began on March 20, 2026. Karatsu is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in August at around 30°C, while the coldest stretch bottoms out in January near 6°C. Summer is next, beginning on June 21, 2026 — 88 days from now.

The best time to visit Karatsu is during October and November, when the weather is most comfortable for travellers. During these months, average temperatures hover around 18°C with modest rainfall averaging 95mm per month. By contrast, August can be uncomfortably hot with highs reaching 30°C, while January is the coldest period with lows dropping to 6°C. Despite being the best months overall, some rain is still likely — pack a waterproof layer and plan a mix of indoor and outdoor activities.

The table below shows monthly climate averages for Karatsu based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.