Monthly weather forecast and climate

Flag of Japan
Flag 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 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 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.

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.

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. Rainfall ranges between 101.6mm (4") to 127mm (5") in most regions except the east. Winter is the sunniest season in the east. Tokyo, the capital, registers cold temperatures between 2.8°C (37°F) and 10°C (50°F), with 6 hours of daily sunshine. The average hourly wind speeds in Tokyo are below 13.7km/h (8.5mph), with a predominantly northern direction.
Temperatures are mild in the zone of 2.2°C (36°F) to 12.8°C (55°F) in Kyushu and Shikoku. In Okinawa, in the south, average temperatures are pleasant between 20.6°C (69.1°F) and 25.6°C (78.1°F), with 101.6mm (4") of rainfall. Only the tropical southern regions offer fair weather in January in Japan.

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). The average seawater temperatures in Sapporo are the coldest of the year at 3.9°C (39°F).
Tokyo and Yokohama are between 2.8°C (37°F) and 10.6°C (51.1°F), with 63.5mm (2.5") of rainfall amid 6 hours of daily sunshine. Okinawa receives between 127mm (5") to 152.4mm (6") of rain and registers average temperatures in the mild 14.4°C (57.9°F) to 21.7°C (71.1°F) range. In Chubu, Kanazawa is the wettest place with 172.7mm (6.8") of rainfall and 914.4mm (36") of snowfall. The relative humidity is in the comfortable zone of 55% to 60% in most regions.
Bring a rain jacket and sweater at a minimum for the south and warm winter clothes for the north. Snow lovers prefer northern Japan in February.

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). Rainfall is in the 50.8mm (2") to 76.2mm (3") range and snowfall measures between 508mm (20") and 1016mm (40").
Tokyo registers between 5.6°C (42.1°F) and 13.3°C (55.9°F), with an average precipitation of 101.6mm (4") to 127mm (5"). The daylight increases to 12 hours by the spring equinox in Tokyo. Chubu sees its last snowfall by mid-March, as the 6 hours of daily sunshine keeps average temperatures in the -0.6°C (30.9°F) to 11.1°C (52°F) zone. March is the windiest month of the year in Osaka, with average hourly wind speeds of 15km/h (9.3mph) to 15.3km/h (9.5mph).
The average seawater temperatures in Okinawa are at a mild 22.2°C (72°F). Warm jackets are useful for protection from cold and rain. March begins to see tourist footfalls across Japan as the weather improves gradually.

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. Tokyo is between 10.6°C (51.1°F) and 17.2°C (63°F), with clear skies for 50% of the time and 13 hours of daylight. The average seawater temperature in Tokyo is at a mild 17.2°C (63°F), and the average hourly wind speeds remain below 14.5km/h (9mph). Takamatsu and Kochi in the Shikoku region have warm temperatures in the 8.9°C (48°F) to 21.1°C (70°F) zone. Kochi receives abundant rainfall of 243.8mm (9.6"). Rain jackets or umbrellas are necessary, with at least 10 wet days in the month.
April is a wonderful time to visit Japan as the cherry blossom season is evident in many regions.

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. Precipitation in Hokkaido is in the 38.1mm (1.5") to 63.5mm (2.5") range. The daily sunshine lasts between 5 hours and 7 hours, and the daylight registers above 14 hours. Temperatures in Fukuyama and Hiroshima are warm between 12.8°C (55°F) and 23.9°C (75°F). In Okinawa, the average temperatures are in the warm 21.1°C (70°F) to 28.3°C (82.9°F) zone, but the sunshine lasts less than 6 hours a day. In the Kyushu region, Kagoshima is warm, with average temperatures in the 17.2°C (63°F) to 25°C (77°F) range.
Monsoon rains reach the southern islands by the fourth week of May. The relative humidity registers between 60% and 70% in Osaka, with overcast skies 55% of the time. May has some of the best conditions to visit Japan.

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. Hokkaido and Tohoku remain warm in the 10°C (50°F) to 23.9°C (75°F) range. June 21 is the longest day during the summer solstice in Tokyo, with 14 hours and 35 minutes of daylight. The relative humidity rises significantly to register between 70% and 80% in most regions. The skies are cloudy between 60% and 70% of the time and limit the daily sunshine to less than 5 hours.
The average seawater temperatures range between 17.2°C (63°F) in the extreme north to 25°C (77°F) in the extreme south. The humidity and rain make June weather unfavorable to visit Japan.

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"). The daily sunshine is short of 5 hours in the north but lasts up to 8 hours on the southern islands.
The average temperatures in Hokkaido in the north register in the 15.6°C (60.1°F) to 25.6°C (78.1°F) range. The average low temperatures are in the 20°C (68°F) to 23.9°C (75°F) zone in Chubu and Kansai. The average high temperatures are between 26.7°C (80.1°F) to 32.2°C (90°F) going from the central to southern regions.
The last week of July is generally the calmest of the year, with average hourly wind speeds between 11.6km/h (7.2mph) and 12.1km/h (7.5mph) in Tokyo. The relative humidity is in the zone of 70% to 85% most of the time. Rainstorms frequently occur in July in Japan.

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. Nights are mild in the extreme north but warm and humid in the rest of Japan.
The northern half receives 76.2mm (3") to 152.4mm (6") of average precipitation. The southern extremes of Okinawa and nearby islands receive heavy rainfall between 254mm (10") to 304.8mm (12") due to the impact of typhoons. August brings 6 hours to 8 hours of daily sunshine in most regions. The eastern region is cloudy and receives only 5 hours of sunshine every day.
August has the warmest seas of the year. The average seawater temperatures range between 21.1°C (70°F) in Sapporo in the north to 28.9°C (84°F) in Naha in Okinawa in the south. The days are muggy, with relative humidity often in the 80% to 95% range. August is a time to avoid long trips to Japan.

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. In Honshu, Aomori receives 124.5mm (4.9") and Niigata 175.3mm (6.9"). Tokyo receives 210.8mm (8.3"), its highest precipitation of the year.
The capital is warm in the 20°C (68°F) to 27.2°C (81°F) range but humid, with hardly 4 hours of daily sunshine. Typhoons hit the southern region to bring 203.2mm (8") to 304.8mm (12") of heavy rainfall. The average temperatures register between 23.9°C (75°F) and 29.4°C (84.9°F) in the central and southern regions.
Okinawa is in mid-summer, in contrast to autumn in the north. The average seawater temperatures register between 23.9°C (75°F) and 25°C (77°F) in Osaka. Keep an eye on the weather for heavy rainfall and strong winds in the south. Expect wet and humid conditions in September.

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. Tohoku is between 8.3°C (46.9°F) and 20.6°C (69.1°F). However, the night temperatures remain above 10°C (50°F) in the central and southern regions. Days are warm in the south, and the warmest temperatures are in Okinawa in the 22.2°C (72°F) to 28.9°C (84°F) range.
The precipitation decreases in the north to register in the 50.8mm (2") to 101.6mm (4") range. The eastern region, including Tokyo, receives ample rainfall between 152.4mm (6") to 228.6mm (9") in October, and is cloudy, with 4 hours of daily sunshine. The central receives 101.6mm (4") to 177.8mm (7"), while the south registers 177.8mm (7") to 228.6mm (9") of rainfall, due to occasional storms. Frost is evident in the extreme north. The daylight begins to decrease and registers below 11 hours by the end of the month.
October is an excellent option for budget travelers to visit southern Japan.

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. Asahikawa registers many nights below freezing. Sendai is cold between 5°C (41°F) and 13.9°C (57°F), while Tokyo is mild between 11.1°C (52°F) and 15.6°C (60.1°F).
Much of the central and eastern regions remain in the 10°C (50°F) to 21.1°C (70°F) zone. Okinawa is the only region with warm temperatures in the 21.1°C (70°F) to 26.7°C (80.1°F). The landscape remains colorful until mid-November, especially in the central and southern regions. The precipitation reduces significantly but registers in the range of 50.8mm (2") to 127mm (5") in most regions. Expect warm days but cold nights and carry a sweater for the north.
The average seawater temperatures register between a cold 12.2°C (54°F) in the north to a warm 25°C (77°F) in the south. November has fair weather in southern Japan at the end of the typhoon season.

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). Asahikawa and Sapporo receive 1320.8mm (52") to 1879.6mm (74") of snowfall. Precipitation is in the average range of 50.8mm (2") to 101.6mm (4"). The central, east, and southern regions receive less than 254mm (10") of snow. Kyoto, Nara, and Osaka in the Kansai region register cold to mild temperatures between 3.3°C (37.9°F) to 10.6°C (51.1°F). December 21 is the shortest day of the year in Osaka, with 9 hours and 50 minutes of daylight.
Warm winter coats are necessary for the freezing nights in the cold regions. Even in Okinawa, where the average sweater temperatures are at a warm 23.9°C (75°F), a sweater or jacket brings comfort. December is generally a time to avoid Japan except for the tropical islands in the south.
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