Climate - Okayama (Japan)

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The climate of Okayama, a Japanese city in the southern part of Honshu Island, in the region called Chogoku, is temperate, with quite mild winters and hot, moist, and rainy summers. Like the rest of Japan, the city is affected by the monsoon circulation: in winter, the northwest cold currents prevail, while in summer, they are replaced by hot and humid currents of tropical origin.
Okayama is located on the coast, in the Seto Inland Sea, an area relatively protected both from the winter monsoon (since we are on the south side) and from the summer monsoon as well as typhoons. In fact, on the other side of the sea, we find the island of Shikoku, which protects it from the south winds with its mountains.
In winter, there are fairly mild periods, with highs above 12 °C (54 °F), alternating with cold periods, with wind, rain, and highs around 5/7 °C (41/45 °F) or less. Night frosts are typically light, both because of the influence of the sea and because of the heat island effect. However, in January 1963, the temperature dropped to -8.9 °C (16 °F). Snowfall is very rare, even more so than in Tokyo.
Summers are hot and humid; there can be periods of good weather, with maximum temperatures around 35 °C (95 °F) or above and high humidity, but also periods of bad weather due to the summer monsoon. August is the hottest month, both because of the thermal inertia of the sea and because of the lower frequency of periods of bad weather.
Here are the average temperatures.

The temperatures of the airport, located north of the city, in a green area, and at 240 meters (800 feet) of altitude, are a bit lower.
Rainfall is quite abundant (although this is one of the driest areas of Japan), in fact it amounts to 1,100 millimeters (43 inches) per year. Winter is undoubtedly the driest season. The rainiest months are June and July, ie the first period of the rainy season (called Baiu). In August, there is a certain decrease in rain frequency: on average, among the summer months, it is the hottest as well as the driest and sunniest.
Here is the average precipitation.

From June to October (but especially from August to early October), Okayama may be affected by typhoons, the tropical cyclones of Southeast Asia, though, as mentioned, this area of the Seto Inland Sea is relatively sheltered.
The cherry blossoming in Okayama occurs around April 3rd.
The main tourist attraction of Okayama, together with the castle, is the Koraku-en, the Japanese garden, considered as one of the three most important, together with the Kenroku-en in Kanazawa and the Kairaku-en in Mito.



The amount of sunshine in Okayama, quite good in winter, never becomes very good, but in summer, it is higher than in other parts of Japan. The sunniest months are April, May and August, with around 6 hours and a half of sunshine per day, and there are more than 2,000 hours of sunshine per year. This area is known to the Japanese as "The Sunny Country", but above all because the rains are relatively scarcer. Here are the average sunshine hours per day.

The sea in Okayama is warm enough for swimming, with a temperature of 23 °C (73 °F) or more, from July to October, and it becomes pleasantly warm in August. Here are the average sea temperatures.

Okayama - Weather by month

Based on the period 1991-2020

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In January, the coldest month of the year, the weather in Okayama is usually quite cold. The average temperature is of 5.2 °C (41 °F), with a minimum of 1.2 °C (34.2 °F) and a maximum of 9.3 °C (48.7 °F).
On the coldest nights of the month, the temperature usually drops to around -2.5 °C (27 °F). However, it dropped to -5.5 °C (22.1 °F) in January 2018.
On the warmest days of the month, the temperature usually reaches around 14 °C (57 °F). However, it reached 16.9 °C (62.4 °F) in January 2016.
Precipitation amounts to 35 mm (1.4 in), distributed over 5 days.
The day lasts on average 10 hours and 5 minutes.
There are on average 5 sunshine hours per day. So, the sun shines 48% of the time.
The average humidity is 69%.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 16 °C (61 °F). Therefore, the sea is cold for swimming.

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In February, the weather in Okayama is usually quite cold. The average temperature is of 6.0 °C (43 °F), with a minimum of 1.6 °C (34.9 °F) and a maximum of 10.3 °C (50.5 °F).
On the coldest nights of the month, the temperature usually drops to around -2.5 °C (28 °F). However, it dropped to -6.1 °C (21 °F) in February 2018.
On the warmest days of the month, the temperature usually reaches around 16.5 °C (62 °F). However, it reached 22.1 °C (71.8 °F) in February 2010.
Precipitation amounts to 45 mm (1.8 in), distributed over 7 days.
The day lasts on average 11 hours and 0 minutes.
There are on average 5 sunshine hours per day. So, the sun shines 47% of the time.
The average humidity is 66%.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 15 °C (59 °F). Therefore, the sea is cold for swimming.

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In March, the weather in Okayama is usually mild. The average temperature is of 9.2 °C (48 °F), with a minimum of 4.4 °C (39.9 °F) and a maximum of 13.9 °C (57 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -0.5 °C (31 °F). However, it dropped to -3.2 °C (26.2 °F) in March 2015.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 21 °C (69.5 °F). However, it reached 24.8 °C (76.6 °F) in March 2018.
Precipitation amounts to 85 mm (3.3 in), distributed over 9 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 5.5 sunshine hours per day. So, the sun shines 48% of the time.
The average humidity is 65%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 15 °C (59 °F). Therefore, the sea is cold for swimming.

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In April, the weather in Okayama is usually very mild. The average temperature is of 14.6 °C (58 °F), with a minimum of 9.5 °C (49.1 °F) and a maximum of 19.8 °C (67.6 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 2.5 °C (37 °F). However, it dropped to 0.3 °C (32.5 °F) in April 1996.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 26.5 °C (79.5 °F). However, it reached 29.6 °C (85.3 °F) in April 2004.
Precipitation amounts to 90 mm (3.5 in), distributed over 10 days.
The day lasts on average 13 hours and 5 minutes.
There are on average 6.5 sunshine hours per day. So, the sun shines 49% of the time.
The average humidity is 60%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 16 °C (61 °F). Therefore, the sea is cold for swimming.

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In May, the weather in Okayama is usually warm. The average temperature is of 19.8 °C (68 °F), with a minimum of 14.7 °C (58.5 °F) and a maximum of 24.9 °C (76.8 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 9 °C (48.5 °F). However, it dropped to 5.7 °C (42.3 °F) in May 1991.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 30.5 °C (87 °F). However, it reached 33.6 °C (92.5 °F) in May 2015.
Precipitation amounts to 115 mm (4.5 in), distributed over 9 days.
The day lasts on average 14 hours and 0 minutes.
There are on average 6.5 sunshine hours per day. So, the sun shines 47% of the time.
The average humidity is 64%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 18.5 °C (65.5 °F). Therefore, the sea is very cool for swimming.

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In June, the weather in Okayama is usually warm to hot. The average temperature is of 23.6 °C (75 °F), with a minimum of 19.5 °C (67.1 °F) and a maximum of 27.8 °C (82 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 15 °C (59 °F). However, it dropped to 11.9 °C (53.4 °F) in June 2016.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 33.5 °C (92 °F). However, it reached 37 °C (98.6 °F) in June 2013.
Precipitation amounts to 170 mm (6.7 in), distributed over 12 days.
The day lasts on average 14 hours and 25 minutes. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
There are on average 5 sunshine hours per day. So, the sun shines 35% of the time.
The average humidity is 71%. Hence, the air is normally humid.
The average wind speed is 7 kph (4 mph).
The average sea temperature is of 22 °C (71 °F). Therefore, the sea is cool for swimming.

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In July, the weather in Okayama is usually very hot. The average temperature is of 27.8 °C (82 °F), with a minimum of 23.9 °C (75 °F) and a maximum of 31.7 °C (89.1 °F).
On the coldest nights of the month, the temperature usually drops to around 20.5 °C (68.5 °F). However, it dropped to 17.3 °C (63.1 °F) in July 1992.
On the warmest days of the month, the temperature usually reaches around 36 °C (97 °F). However, it reached 38.1 °C (100.6 °F) in July 2018.
Precipitation amounts to 175 mm (6.9 in), distributed over 11 days.
The day lasts on average 14 hours and 10 minutes.
There are on average 5.5 sunshine hours per day. So, the sun shines 39% of the time.
The average humidity is 74%. Hence, the air is normally humid.
The average wind speed is 7 kph (4 mph).
The average sea temperature is of 25 °C (77 °F). Therefore, the sea is warm enough for swimming.

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In August, the warmest month of the year, the weather in Okayama is usually very hot. The average temperature is of 29.0 °C (84 °F), with a minimum of 24.9 °C (76.8 °F) and a maximum of 33 °C (91.4 °F).
On the coldest nights of the month, the temperature usually drops to around 21 °C (70 °F). However, it dropped to 17.3 °C (63.1 °F) in August 2018.
On the warmest days of the month, the temperature usually reaches around 36.5 °C (97.5 °F). However, it reached 39.3 °C (102.7 °F) in August 1994.
Precipitation amounts to 95 mm (3.7 in), distributed over 8 days.
The day lasts on average 13 hours and 25 minutes.
There are on average 6.5 sunshine hours per day. So, the sun shines 49% of the time.
The average humidity is 69%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 27.5 °C (81 °F). Therefore, the sea is pleasantly warm and allows long swims.

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In September, the weather in Okayama is usually warm to hot. The average temperature is of 24.8 °C (77 °F), with a minimum of 20.8 °C (69.4 °F) and a maximum of 28.7 °C (83.7 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 15 °C (59 °F). However, it dropped to 11.5 °C (52.7 °F) in September 1992.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 33.5 °C (92.5 °F). However, it reached 37.1 °C (98.8 °F) in September 2020.
Precipitation amounts to 140 mm (5.5 in), distributed over 10 days.
The day lasts on average 12 hours and 25 minutes.
There are on average 5 sunshine hours per day. So, the sun shines 42% of the time.
The average humidity is 71%. Hence, the air is normally humid.
The average wind speed is 7 kph (4 mph).
The average sea temperature is of 26 °C (79 °F). Therefore, the sea is warm enough for swimming.

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In October, the weather in Okayama is usually warm. The average temperature is of 18.7 °C (66 °F), with a minimum of 14.4 °C (57.9 °F) and a maximum of 23 °C (73.4 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 8 °C (46.5 °F). However, it dropped to 2.5 °C (36.5 °F) in October 2020.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 28.5 °C (83.5 °F). However, it reached 33.4 °C (92.1 °F) in October 2018.
Precipitation amounts to 95 mm (3.7 in), distributed over 8 days.
The day lasts on average 11 hours and 20 minutes.
There are on average 5.5 sunshine hours per day. So, the sun shines 49% of the time.
The average humidity is 71%. Hence, the air is normally humid.
The average wind speed is 7 kph (4 mph).
The average sea temperature is of 23.5 °C (74 °F). Therefore, the sea can be considered barely acceptable for swimming.

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In November, the weather in Okayama is usually mild. The average temperature is of 12.7 °C (55 °F), with a minimum of 8.3 °C (46.9 °F) and a maximum of 17.1 °C (62.8 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 2.5 °C (36.5 °F). However, it dropped to 0.3 °C (32.5 °F) in November 2013.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 22.5 °C (72 °F). However, it reached 24.6 °C (76.3 °F) in November 2020.
Precipitation amounts to 55 mm (2.2 in), distributed over 6 days.
The day lasts on average 10 hours and 20 minutes.
There are on average 5 sunshine hours per day. So, the sun shines 50% of the time.
The average humidity is 72%. Hence, the air is normally humid.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 21 °C (70 °F). Therefore, the sea is cool for swimming.

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In December, the weather in Okayama is usually quite mild. The average temperature is of 7.4 °C (45 °F), with a minimum of 3.3 °C (37.9 °F) and a maximum of 11.6 °C (52.9 °F).
On the coldest nights of the month, the temperature usually drops to around -1 °C (30.5 °F). However, it dropped to -2.7 °C (27.1 °F) in December 2013.
On the warmest days of the month, the temperature usually reaches around 16.5 °C (62 °F). However, it reached 20.6 °C (69.1 °F) in December 2018.
Precipitation amounts to 40 mm (1.6 in), distributed over 6 days.
The day lasts on average 9 hours and 55 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
There are on average 5 sunshine hours per day. So, the sun shines 50% of the time.
The average humidity is 71%. Hence, the air is normally humid.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 18.5 °C (65 °F). Therefore, the sea is very cool for swimming.