Monthly weather forecast and climate

Flag of Japan
Flag of Japan

The climate of Japan

Japan has a mainly temperate climate, ranging from cold in the north to subtropical in the south. The climate varies from humid continental (Köppen climate classification Dfb) in the north to tropical rainforest and tropical monsoon in the south (Köppen Af, Am). Most regions in central and southern Japan experience a humid subtropical climate (Köppen Cfa). The mountains in the central highlands display an alpine climate (Köppen ET) at high altitudes. Japan is an island country in East Asia along the Pacific Coast, with a northeast-southwest orientation. The Russian Far East lies across the Sea of Okhotsk in the north, the Pacific Ocean is in the east, China and Taiwan are across the East China Sea in the southwest, and the Korean Peninsula is in the west across the Sea of Japan. The latitudes, proximity to vast bodies of water, high mountain ranges, and ocean currents influence the climate.

Japan is an archipelago of volcanic islands 20°N to 45°N of the equator. The country has a long coastline of 18,486 miles along with numerous outlying islands. The rugged terrain comprises 73% mountainous regions, and 66% of the total area consists of forests. Hokkaido, Honshu, Kyushu, Shikoku, and Okinawa are the 5 major islands. Each main island has a mountain range. The Hida, Kiso, and Akaishi mountain chains converge in central Japan. The Kanto, Nobi, and Osaka are the three largest plains in central Honshu. Numerous hot springs dot the country. Rivers are deep and swift. The Shinano River is the longest river with a length of 228 miles. The tallest peak in Japan at the height of 3776 meters is Mount Fuji, a dormant volcano. Lake Hachirogata is the lowest point at 4 meters below sea level. No point in Japan lies more than 93 miles from the sea. Eight warm and cold ocean currents surround the Japanese archipelago.

Summers are cool in Hokkaido in northern Japan, but hot and wet in the south. The average summer temperature is 25.2°C (77.4°F). Winters are cold in the north but mild in the south. The average winter temperature is 5.1°C (41.2°F). Snowfall is abundant in northern areas of Hokkaido, such as Sapporo and Asahikawa. The northwest wind brings heavy snowfall in the Sea of Japan region. Foehn winds occasionally bring high temperatures. The Central Highlands show significant variations between the hot summer and moderate winter temperatures. Precipitation is lower than the coast. In the Seto Inland Sea area, mountains block seasonal winds and keep the climate mild. Summers are hot on the Pacific Coast in the southeast. Ryuku Islands have hot summers and mild winters. The rainy season begins in May in the south and July in the north. Late summer and early autumn receive heavy rainfall due to typhoons.

The average annual rainfall in Japan ranges from 1016mm (40") to 2540mm (100"). The country is wet and humid. Precipitation occurs throughout the year, but the rainiest period is between June and August. The rain shadow regions of Nagano and Yamanishi receive 762mm (30") to 889mm (35") of precipitation. Yakushima Island is the wettest place in Japan, with annual precipitation between 4064mm (160") and 10160mm (400"). Typhoons bring heavy rainfall between July and October. The annual sunshine is in the modest range of 1600 hours to 2200 hours. The Sea of Japan coast in Hokkaido receives the least daily average sunshine of 4 hours. The Pacific coast in the south registers the highest daily average sunshine of 6 hours. The central mountain ranges facing the Sea of Japan receive the highest snowfall. Aomori, in the Tohoku region, with 6680.2mm (263") of snowfall annually, is one of the snowiest cities on the plains in the world.

The highest temperature on record for Japan is 41.1°C (106°F), set in Kumagaya, Saitama, on July 23, 2018. The record for the lowest temperature is -41°C (-41.8°F), set in Asahikawa, Hokkaido, on January 25, 1902.

The best time to visit Japan

The best time to visit Japan is in the spring season from April to early June. May is perfect for witnessing the cherry blossoms in most regions. The climate is temperate, and the atmosphere is relatively dry, although much of Japan receives 25.4mm (1") to 101.6mm (4") of rain every month. The average temperatures range between 17.2°C (63°F) in the north and 27.2°C (81°F) in the south. The days are warm, with moderate sunshine, while the nights are mild to cold. April is a comfortable month to visit the south, such as Okinawa. Snow melts in most regions by the beginning of April.

The worst time to visit Japan

The worst time to visit Japan is from late June to August in the summer season. The rainy season occurs during the period, and the atmosphere is humid, cloudy, and hot. Temperatures above 37.8°C (100°F) and significant humidity keep the heat index high. The islands receive heavy rainfall, particularly the southern ones. Typhoons frequent the coasts, as the storm season begins by early summer. At least 5 typhoons visit the Japanese coasts in the summer. Rainstorms occur regularly and cause floods and mudslides. Okinawa and Anami see the peak of the tropical storm season in August.

Weather hazards

Japan lies in the Pacific Ring of Fire and faces weather hazards such as thunderstorms, floods, earthquakes, tsunamis, and volcanic eruptions. Japan has 108 active volcanoes. The entire country is prone to frequent seismic activities. Large earthquakes generate tsunamis. Major earthquakes, such as in Tokyo in 1923, Hanshin in 1995, Tohoku in 2011, occur periodically. Typhoons frequently occur in the Northwestern Pacific Basin during the storm season from May to November. Tropical storms and typhoons average 15 to 20 in a year and frequently make landfalls. Strong winds above 241.4km/h (150mph) and torrential rainfall cause large-scale damage during typhoons. Thunderstorms frequently occur in the rainy season.

Weather in January

January is the peak of the winter in Japan, with cloudy and dark skies. The temperatures drop below freezing in the north. In interior Hokkaido, the average temperatures are at a frigid -10°C (14°F). Aomori, on the northern tip of Honshu, is cold between -3.9°C (25°F) and 2.2°C (36°F), and dark with hardly 2 hours of daily sunshine. The western side, particularly near the Sea of Japan, is prone to heavy snowfall and rain. Weather in January »

Weather in February

February is a cold winter month in Japan. The cold Siberian air masses penetrate the north to bring frigid temperatures below 0°C (32°F) and dark skies. Abashiri and Sapporo hold ice festivals, with 1016mm (40") to 1727.2mm (68") of snowfall and average temperatures in the icy zone of -10°C (14°F) to 0°C (32°F). Weather in February »

Weather in March

March sees the arrival of the spring season in southern Japan, with an increase in daily sunshine to 5 hours. The northern cities of Hokkaido, such as Abashiri, Asahikawa, and Sapporo, are still cold, with average temperatures between -6.1°C (21°F) and 3.9°C (39°F). Weather in March »

Weather in April

April is mild to warm in the spring season in Japan, with daily sunshine up to 6 hours. The snow thaws in the north, and nights are above freezing. The average temperatures in Fukushima and Sendai in the Tohoku region register in the mild 6.1°C (43°F) to 17.2°C (63°F) range. Precipitation is between 76.2mm (3") and 152.4mm (6") in the north and central parts and 152.4mm (6") to 228.6mm (9") in the southern islands. Weather in April »

Weather in May

May is warm in Japan and relatively dry in the northern regions. The cherry blossom occurs in the first week of May in Sapporo, where average temperatures are between 7.8°C (46°F) and 17.2°C (63°F). Snow is absent on the ground. Weather in May »

Weather in June

June is hot, humid, and the wettest month in southern Japan. The rainy season begins earnestly to bring 254mm (10") to 431.8mm (17") of precipitation in the southern regions. The extreme north receives 76.2mm (3") to 127mm (5"), while the central regions register 127mm (5") to 254mm (10"). The average temperatures are between 18.3°C (64.9°F) to 26.7°C (80.1°F) in the central and 24.4°C (75.9°F) to 30.6°C (87.1°F) in the southern islands. Weather in June »

Weather in July

July is hot and humid in Japan, with a generally wet and cloudy atmosphere. The monsoon reaches the hinterland and brings 101.6mm (4") to 177.8mm (7") of rain in the northern islands. The rainfall increases progressively in the south up to Kyushu, which receives 254mm (10") to 381mm (15"), while Okinawa registers 127mm (5") to 152.4mm (6"). Weather in July »

Weather in August

August is usually the hottest month in Japan, with cloudy skies. The average high temperatures register between 22.2°C (72°F) and 26.7°C (80.1°F) in Hokkaido in the north and 30.6°C (87.1°F) and 33.3°C (91.9°F) in the southern half. Weather in August »

Weather in September

September is hot and humid in central and southern Japan but mild in the north. The moderate sunlight lasts up to 5 hours in Hokkaido and Honshu and 7 hours in Okinawa. September is the rainiest month in the extreme north, with 109.2mm (4.3") to 134.6mm (5.3") of rainfall in Abashiri and Sapporo. Weather in September »

Weather in October

October brings mild to warm conditions in much of Japan except the extreme south. The fall foliage is at its peak, and the humidity and rainfall are relatively less. Hokkaido registers average temperatures in the 3.9°C (39°F) to 16.1°C (61°F) range, with nights mostly above freezing. Weather in October »

Weather in November

November is cold in the autumn in Japan, with a gradual increase in cloud cover and a decrease in the sunshine. The average temperatures are in the cold zone of 0°C (32°F) to 7.8°C (46°F) in the extreme north. Sapporo and Wakkanai register first snowfall by mid-November. Weather in November »

Weather in December

December is the beginning of the harsh winter in Japan, particularly in the north. Cloudy skies, heavy snowfall, and rain keep the conditions dull and dark. The daily sunshine reduces to 2 hours in most regions except in the east, where winter is the sunniest season. The average temperatures in the extreme north are in the cold range of -7.8°C (18°F) to 3.3°C (37.9°F). Weather in December »

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