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Monthly climate in Koshima, Japan

Last updated: July 31, 2025

Under the Köppen–Geiger climate classification Koshima features a humid subtropical climate (Cfa). Temperatures typically range between 14 °C (57 °F) and 28 °C (82 °F) through the year, but rarely can drop to 6 °C (44 °F) or can rise to as high as 30 °C (86 °F). The average annual precipitation amounts to about 2623 mm (103.3 inches) and receives 181 rainy days on the 1 mm (0.04 inches) threshold annually. Koshima enjoys an average of 3041 hours of sunshine throughout the year, and daylight varies from 10 hours 13 minutes to 14 hours 2 minutes per day.

Monthly average temperatures in Koshima, Japan

The warmest months in Koshima are July, August and September, with daily mean temperatures ranging from 27 to 28 °C (80 - 82 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 14 to 16 °C (57 - 61 °F) throughout the day. On average each year, Koshima experiences 101 days above 25 °C (77.0 °F) and 0 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Koshima. Generated using Copernicus Climate Change Service information. Data for period from January 2017 to June 2022.
 JanFebMarAprMayJunJulAugSepOctNovDec
Maximum21°C
(70°F)		21°C
(70°F)		22°C
(72°F)		24°C
(75°F)		26°C
(78°F)		27°C
(81°F)		30°C
(86°F)		30°C
(86°F)		29°C
(84°F)		27°C
(81°F)		25°C
(78°F)		24°C
(75°F)
Mean maximum20°C
(68°F)		20°C
(68°F)		21°C
(70°F)		22°C
(73°F)		25°C
(77°F)		26°C
(79°F)		29°C
(84°F)		29°C
(85°F)		29°C
(84°F)		27°C
(81°F)		24°C
(75°F)		22°C
(71°F)
Average high15°C
(60°F)		15°C
(60°F)		18°C
(64°F)		20°C
(68°F)		23°C
(73°F)		25°C
(77°F)		28°C
(82°F)		28°C
(83°F)		27°C
(81°F)		24°C
(76°F)		21°C
(70°F)		17°C
(63°F)
Daily mean14°C
(57°F)		14°C
(57°F)		16°C
(62°F)		19°C
(66°F)		22°C
(71°F)		24°C
(76°F)		27°C
(81°F)		28°C
(82°F)		27°C
(80°F)		24°C
(75°F)		20°C
(68°F)		16°C
(61°F)
Average low13°C
(55°F)		12°C
(54°F)		15°C
(60°F)		18°C
(64°F)		21°C
(70°F)		23°C
(74°F)		26°C
(80°F)		27°C
(81°F)		26°C
(79°F)		23°C
(74°F)		19°C
(66°F)		14°C
(58°F)
Mean minimum8°C
(47°F)		8°C
(47°F)		11°C
(52°F)		13°C
(56°F)		17°C
(63°F)		20°C
(69°F)		24°C
(76°F)		26°C
(78°F)		23°C
(74°F)		19°C
(66°F)		14°C
(58°F)		9°C
(49°F)
Minimum6°C
(44°F)		7°C
(44°F)		10°C
(51°F)		12°C
(53°F)		16°C
(61°F)		19°C
(67°F)		23°C
(73°F)		24°C
(76°F)		22°C
(72°F)		18°C
(65°F)		13°C
(56°F)		8°C
(46°F)

Compare climate in Koshima with other places

Compare temperature, precipitation, sunshine, UV index in Koshima, Japan with other places around the world.

Monthly average precipitation in Koshima, Japan

Koshima usually has the most precipitation in May, June and July, with an average of 16 rainy days and 348 mm (13.7 inches) of precipitation per month. The driest months in Koshima are January, November and December. On average, 130 mm (5.1 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Koshima. Generated using Copernicus Climate Change Service information. Data for period from January 2017 to January 2022.
 JanFebMarAprMayJunJulAugSepOctNovDec
Average precipitation mm (inches)108 (4.2)157 (6.2)213 (8.4)186 (7.3)273 (10.7)491 (19.3)281 (11.0)214 (8.4)256 (10.1)164 (6.4)150 (5.9)132 (5.2)
Average precipitation days (≥ 1 mm)121616121319171620131314

Monthly sunshine hours in Koshima, Japan

The sunniest months in Koshima are July, August and September, when the sun shines an average of 9 hours 50 minutes a day. Least sunny months in Koshima: January, February and December receive an average of 6 hours 25 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Koshima. Generated using Copernicus Atmosphere Monitoring Service information. Data for period from January 2017 to January 2022.
 JanFebMarAprMayJunJulAugSepOctNovDec
Mean monthly sunshine hours163216253272279242301319283265238204
Mean daily daylight hours10h 25m11h 6m11h 59m12h 54m13h 40m14h 2m13h 51m13h 11m12h 19m11h 24m10h 37m10h 13m

Solar UV radiation in Koshima, Japan

Koshima experiences the highest level of ultraviolet (UV) radiation in May, July and August, when the maximum UV index can reach values of 12 - 13, which corresponds to the Extreme category of sun exposure. January, February and December are in the Moderate / High exposure category. In these months, the maximum values of the UV index do not exceed 7. For more detailed information, check out our hourly Koshima UV Index data.

Average daily maximum UV levels by month for Koshima. Generated using Copernicus Atmosphere Monitoring Service information. Data for period from January 2022 to January 2023.
 JanFebMarAprMayJunJulAugSepOctNovDec
UV Index (month maximum)5710111212131311875