Japan runs a long way from north to south, so the same month can feel very different in Hokkaido and in Okinawa. The figures here are the Japan Meteorological Agency’s normals, the average of 30 years of observations from 1991 to 2020.
Temperature by month
Cold → Hot Top: average high / bottom: average low (°C)
Japan Meteorological Agency normals for 1991-2020 at each city's observatory, rounded to whole degrees.
Tokyo, Osaka and Fukuoka follow much the same curve, and in midsummer the night-time low stays around 25°C. Sapporo’s lows are below freezing from December to March, while Naha’s daytime high is 20°C even in January.
Rainfall by month
Dry → Wet Monthly rainfall (mm)
Japan Meteorological Agency normals for 1991-2020. Most of Sapporo's winter precipitation falls as snow.
Tokyo and Osaka have their lowest rainfall from December to February. Sapporo has no rainy season, and its precipitation rises in winter as snow.
Rainy season
Rainy season starts Rainy season ends
Japan Meteorological Agency normals for 1991-2020 (approximate dates). No start or end is announced for Hokkaido.
The start and end are dates the Japan Meteorological Agency announces from each year’s weather, so many years run one or two weeks earlier or later than normal. The end of the rainy season marks the start of the full summer heat.
Typhoon season
Japan Meteorological Agency normals for 1991-2020: typhoons passing within 300 km of the main islands (Hokkaido, Honshu, Shikoku, Kyushu). Okinawa and Amami see 7.9 a year.
When a typhoon approaches, flights, Shinkansen and ferries can stop or run late. Okinawa sees typhoons more often than the main islands, from May to November.
