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Karatsu, Saga Weather by Month and Climate Averages
Monthly normals · Rain · Snow
Sunshine · Freeze dates · Records · Best time to visit
What is the weather like in Karatsu, Saga?
Karatsu, Saga gets 1765 mm of precipitation a year over about 105 rainy days. August is the warmest month (average high 33°C) and January the coldest (average low 1°C).
Humid subtropical climate
Karatsu, Saga has hot summers and chilly winters. Daytime highs range from about 10°C in January to 33°C in August. July is usually the wettest month. The most comfortable time to visit is typically April to May and October to November, when daytime highs sit near 22°C.
| Season | Months | Avg low | Avg high |
|---|---|---|---|
| Winter | Dec–Feb | 2° | 12° |
| Spring | Mar–May | 9° | 21° |
| Summer | Jun–Aug | 23° | 31° |
| Autumn | Sep–Nov | 14° | 24° |
How much rain does Karatsu get?
Karatsu gets 1765 mm of precipitation in an average year, spread over about 105 days with measurable rain. That is fewer rainy days than 62% of Japan.
July is the wettest month, with 341 mm. January is the driest, with 51 mm. June has the most rainy days, about 12.
The longest dry spell in the last five years lasted 18 days, to July 25, 2026.
From October 2025 to September 2026 Karatsu got 2728 mm of rain, against a normal of 1765 mm for those months. September 2026 had the most, with 1555 mm.
Karatsu weather by month
Karatsu weather in January
In January, Karatsu averages a high of 10°C and a low of 1°C. It gets 51 mm of precipitation over about 8 rainy days. Estimated sunshine is 34% of daylight hours, derived from ERA5 cloud cover. The January record high is 21°C (1980) and the record low is -7°C (2016).
Karatsu weather in February
In February, Karatsu averages a high of 12°C and a low of 2°C. It gets 68 mm of precipitation over about 8 rainy days. Estimated sunshine is 36% of daylight hours, derived from ERA5 cloud cover. The February record high is 23°C (2004) and the record low is -6°C (1977).
Karatsu weather in March
In March, Karatsu averages a high of 16°C and a low of 4°C. It gets 105 mm of precipitation over about 10 rainy days. Estimated sunshine is 37% of daylight hours, derived from ERA5 cloud cover. The March record high is 26°C (2023) and the record low is -4°C (1977).
Karatsu weather in April
In April, Karatsu averages a high of 21°C and a low of 9°C. It gets 147 mm of precipitation over about 8 rainy days. Estimated sunshine is 39% of daylight hours, derived from ERA5 cloud cover. The April record high is 31°C (1998) and the record low is -1°C (1972). April is one of the most comfortable months to visit.
Karatsu weather in May
In May, Karatsu averages a high of 26°C and a low of 14°C. It gets 167 mm of precipitation over about 8 rainy days. Estimated sunshine is 36% of daylight hours, derived from ERA5 cloud cover. The May record high is 36°C (2000) and the record low is 7°C (1971). May is one of the most comfortable months to visit.
Karatsu weather in June
In June, Karatsu averages a high of 28°C and a low of 19°C. It gets 300 mm of precipitation over about 12 rainy days. Estimated sunshine is 25% of daylight hours, derived from ERA5 cloud cover. The June record high is 37°C (2004) and the record low is 11°C (1972).
Karatsu weather in July
In July, Karatsu averages a high of 32°C and a low of 24°C. It gets 341 mm of precipitation over about 12 rainy days. Estimated sunshine is 25% of daylight hours, derived from ERA5 cloud cover. The July record high is 39°C (1994) and the record low is 16°C (1982).
Karatsu weather in August
In August, Karatsu averages a high of 33°C and a low of 24°C. It gets 210 mm of precipitation over about 10 rainy days. Estimated sunshine is 43% of daylight hours, derived from ERA5 cloud cover. The August record high is 39°C (2026) and the record low is 18°C (1972).
Karatsu weather in September
In September, Karatsu averages a high of 29°C and a low of 21°C. It gets 156 mm of precipitation over about 9 rainy days. Estimated sunshine is 42% of daylight hours, derived from ERA5 cloud cover. The September record high is 37°C (2024) and the record low is 9°C (1987).
Karatsu weather in October
In October, Karatsu averages a high of 24°C and a low of 14°C. It gets 88 mm of precipitation over about 6 rainy days. Estimated sunshine is 53% of daylight hours, derived from ERA5 cloud cover. The October record high is 33°C (2016) and the record low is 3°C (1970). October is one of the most comfortable months to visit.
Karatsu weather in November
In November, Karatsu averages a high of 18°C and a low of 8°C. It gets 75 mm of precipitation over about 7 rainy days. Estimated sunshine is 48% of daylight hours, derived from ERA5 cloud cover. The November record high is 29°C (2023) and the record low is -1°C (1976). November is one of the most comfortable months to visit.
Karatsu weather in December
In December, Karatsu averages a high of 12°C and a low of 3°C. It gets 55 mm of precipitation over about 7 rainy days. Estimated sunshine is 36% of daylight hours, derived from ERA5 cloud cover. The December record high is 24°C (2018) and the record low is -4°C (1973).
Sunshine, humidity and wind in Karatsu
October is the sunniest month in Karatsu, with estimated sunshine of 53% of daylight hours from ERA5 cloud cover. June is the cloudiest, at 25%. The annual cloud-cover estimate is 38% of daylight hours; it is not a measurement of sunshine duration. Karatsu is cloudier than 54% of Japan.
Humidity peaks in July at 84% and is lowest in December at 65%.
Karatsu has about 39 days a year above 32°C. Karatsu is hotter than 94% of Japan.
First and last freeze in Karatsu
The first fall freeze in Karatsu typically comes around December 17, and the last spring freeze around March 4. That leaves a frost-free growing season of about 288 days.
Karatsu weather records
These records cover SAGA during 1970–2026. Earlier records or other stations in the city may differ.
The hottest temperature on record at the Karatsu station is 39°C, on July 16, 1994. The coldest is -7°C, on January 25, 2016.
The wettest day in the available station history brought 456 mm of precipitation, on August 27, 2026.
44 all-time records have been set at the station since 1970.
The best time to visit Karatsu
The most comfortable time to visit is typically April to May and October to November, when daytime highs sit near 22°C.
Winter (December–February) is chilly, with average highs around 12°C and lows near 2°C.
Spring (March–May) is warm, with average highs around 21°C and lows near 10°C.
Summer (June–August) is hot, with average highs around 31°C and lows near 23°C. It can feel humid.
Autumn (September–November) is warm, with average highs around 24°C and lows near 14°C.
Monthly climate
| Month | Average low | Average high | Precip | Rain days | Humidity | Estimated sunshine | Record high | Record low |
|---|---|---|---|---|---|---|---|---|
| January | 1° | 10° | 51 mm | 8 | 67% | 34% | 21° | -7° |
| February | 2° | 12° | 68 mm | 8 | 67% | 36% | 23° | -6° |
| March | 4° | 16° | 105 mm | 10 | 70% | 37% | 26° | -4° |
| April | 9° | 21° | 147 mm | 8 | 71% | 39% | 31° | -1° |
| May | 14° | 26° | 167 mm | 8 | 76% | 36% | 36° | 7° |
| June | 19° | 28° | 300 mm | 12 | 83% | 25% | 37° | 11° |
| July | 24° | 32° | 341 mm | 12 | 84% | 25% | 39° | 16° |
| August | 24° | 33° | 210 mm | 10 | 81% | 43% | 39° | 18° |
| September | 21° | 29° | 156 mm | 9 | 78% | 42% | 37° | 9° |
| October | 14° | 24° | 88 mm | 6 | 70% | 53% | 33° | 3° |
| November | 8° | 18° | 75 mm | 7 | 68% | 48% | 29° | -1° |
| December | 3° | 12° | 55 mm | 7 | 65% | 36% | 24° | -4° |
Station: SAGA, 36 km from the city. Temperature normal baseline: 1991–2020, calculated from available NOAA GHCN-Daily observations. Available station history: 1970–2026; record values refer to this station and period, not the entire city’s history. Precipitation includes rain and the water equivalent of frozen precipitation; snowfall depth is shown separately when available. Sources and methods
From ERA5 reanalysis. Sunshine is estimated from cloud cover.
Karatsu climate questions
How much rain does Karatsu get?
Karatsu gets 1765 mm of precipitation in an average year, over about 105 rainy days.
What is the wettest month in Karatsu?
July is the wettest month in Karatsu, with 341 mm. January is the driest, with 51 mm.
How many rainy days does Karatsu have a year?
Karatsu has about 105 days with measurable rain in an average year. June has the most, about 12.
What is the hottest month in Karatsu?
August is the warmest month in Karatsu, with an average high of 33°C.
What is the coldest month in Karatsu?
January is the coldest month in Karatsu, with an average low of 1°C.
What is the record high temperature in Karatsu?
Within the available 1970–2026 station history, the record high at the Karatsu station is 39°C, set on July 16, 1994. The record low is -7°C, on January 25, 2016.
What is the sunniest month in Karatsu?
October is the sunniest month in Karatsu, with estimated sunshine of 53% of daylight hours from ERA5 cloud cover. June is the cloudiest.
When is the first frost in Karatsu?
The first fall freeze in Karatsu typically comes around December 17. The last spring freeze is around March 4.
What is the best time to visit Karatsu?
The most comfortable time to visit is typically April to May and October to November, when daytime highs sit near 22°C.