Shizuoka City gets 2.4 times the rain of Nagano City, on almost the same number of rainy days

Shizuoka City and Nagano City are the capitals of neighbouring prefectures, yet the rain they get in a year is very different. Using the Japan Meteorological Agency's climate normals (the 1991–2020 average), we look at where and when they differ.

2.4 times the rain

Shizuoka City gets 2,327.3 mm of precipitation a year and Nagano City gets 965.1 mm, a difference of 1,362.2 mm.

Almost the same number of rainy days

Yet the number of days with rain or snow is 106.1 日 in Shizuoka City and 109.6 日 in Nagano City. They hardly differ, and Nagano City even has 3.5 日 more. With the same number of wet days but more rain, Shizuoka City simply gets much more rain on each of those days.

Why Shizuoka gets so much rain

According to the Shizuoka Local Meteorological Office, warm, moist air flows in from the south and rain starts mainly over the mountains. Moist air from the ocean is pushed up against the mountains and falls as rain.

Nagano Prefecture, by contrast, is far from the sea and surrounded by mountain ranges. The Nagano Local Meteorological Office describes an inland climate that is relatively sheltered from typhoons, low-pressure systems and fronts, and calls the area from the Nagano Basin to the Ueda and Saku basins one of the driest in Japan after eastern Hokkaido.

Even more on the mountains

Within Shizuoka City, Ikawa in the mountains to the north gets 3,258.6 mm. In Nagano Prefecture, Mt. Ontake, high in the southwest, gets 3,717.1 mm, 1.6 times Shizuoka City. "Shizuoka is wet, Nagano is dry" is about where the station is, not about the prefecture.

Stations in Nagano's basins are all on the dry side: Matsumoto gets 1,045.1 mm, Saku 964.0 mm and Ueda 906.2 mm.

In winter, the wet days flip

In winter (December–February, 1991–2020), Nagano City has 27.6 日 with precipitation and Shizuoka City has 16.5 日. Only in winter does Nagano City get 1.7 times as many wet days.

Even in winter, though, Shizuoka City gets 265.6 mm and Nagano City gets 153.1 mm, so Shizuoka City still gets more. Nagano City's winter has many days of a little precipitation.

In winter, the northwest monsoon picks up moisture over the Sea of Japan and forms snow clouds that drop snow when they hit the mountains on the Sea of Japan side. Having lost its snow, the air comes down the other side dry, so the Pacific side is sunny and dry. In Nagano Prefecture too, the north has many snowy days while the plains in the centre and south stay sunny.

Takada in Joetsu, Niigata, near the Sea of Japan, gets 2,837.1 mm a year, 475.5 mm of it in December, 1991–2020 alone. Nozawa Onsen in northern Nagano has 89.8 日 with precipitation in the cold season (November–March, 1991–2020).

Mountains make the difference elsewhere too

Kochi (2,666.4 mm), south of the Shikoku Mountains, and Okayama (1,143.1 mm), on the Seto Inland Sea side to the north, differ by 2.3 times. The JMA's notes on Shikoku's climate say warm, moist air from the south is lifted by the Shikoku Mountains, bringing heavy rain to the Pacific side, while the Seto Inland Sea side, sheltered by the mountains, gets less.

Indicator

Annual precipitation normal (mm)

Period

1991–2020

What the value is

Values at a single weather station

Calculation

value as published

Data retrieved

September 29, 2026

Source

Japan Meteorological Agency, "Climatological Normals", "Station history" and "Past weather data", processed by datapictlab

Indicator

Winter precipitation days normal (日)

Period

December–February, 1991–2020

What the value is

Values at a single weather station

Calculation

Sum of monthly normals

Data retrieved

September 29, 2026

Source

Japan Meteorological Agency, "Climatological Normals", "Station history" and "Past weather data", processed by datapictlab