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Hourly Forecast
Daylight Hours
05:38
Sunrise
17:37
Sunset
Moon
Waxing Gibbous
14:50
Moonrise
00:37
Moonset
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View stargazing scoreWeather in Karuizawa today, September 21, 2026
Karuizawa starts September 21, 2026 looking damp, with rain in the forecast and wetter spells likely at times. Waterproof kit is the safer call for early plans. Morning plans should assume damp conditions, as rain chances climb toward 100% around 10:00. Cloud cover is also at its densest near 08:00 at roughly 100%.
The day peaks near 20°C and cools toward 16°C. The air stays humid, with relative humidity between 92% and 98% and the peak around 08:00. Winds stay light, near 4.2 km/h by 23:00, so the day feels still more than breezy.
Through the afternoon wet weather remains a factor, with rain chances near 100% around 12:00. Cloud also stays substantial, close to 100% near 12:00. Horizontal visibility sits around 5.7 km, briefly nearer 0.6 km. Sunrise is at 05:38 and sunset at 17:37, giving 11 hours 58 minutes of sunlight today.
Taken together, Karuizawa looks wet enough on September 21, 2026 that flexible outdoor plans work best, with temperatures peaking near 20°C.
Frequently asked questions about weather in Karuizawa
How warm does it get in Karuizawa?
The warmest month in Karuizawa is August, with average high temperatures of 27°C. The average temperature during this period is around 24°C.
How cold does it get in Karuizawa?
The coldest month in Karuizawa is January, with average low temperatures of -3°C. The average temperature during this period is around 0°C.
What is the wettest time of year in Karuizawa?
The wettest month in Karuizawa is July, with an average of 297mm of precipitation.
What is the driest time of year in Karuizawa?
The driest month in Karuizawa is December, with an average of 43mm of precipitation.
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