Karatsu climate
Karatsu (Japan) has a humid subtropical climate (Köppen Cfa). The average temperature over the year is 17 °C63 °F, and about 1,963 mm77 in of precipitation falls in an average year.
Temperature by month
Precipitation by month
Karatsu climate table
| Month | High °C°F | Low °C°F | Mean °C°F | Precip. mmin | Frost days |
|---|---|---|---|---|---|
| Jan | 1049 | 542 | 846 | 692.7 | 0 |
| Feb | 1151 | 643 | 847 | 893.5 | 0 |
| Mar | 1356 | 847 | 1151 | 1244.9 | 0 |
| Apr | 1864 | 1253 | 1559 | 1586.2 | 0 |
| May | 2271 | 1660 | 1966 | 1746.9 | 0 |
| Jun | 2577 | 2067 | 2272 | 28811 | 0 |
| Jul | 2883 | 2475 | 2679 | 34714 | 0 |
| Aug | 3086 | 2577 | 2882 | 2289.0 | 0 |
| Sep | 2780 | 2272 | 2476 | 1967.7 | 0 |
| Oct | 2272 | 1864 | 2068 | 1114.4 | 0 |
| Nov | 1763 | 1355 | 1559 | 953.7 | 0 |
| Dec | 1253 | 846 | 1050 | 833.2 | 0 |
| Year | 3086 | 542 | 1763 | 1,96377 | 1 |
“Year” row: highest monthly high, lowest monthly low, annual mean and annual total. Frost days are for the whole grid cell.
| Month | Humid. | Cloud | Solar | Daylight |
|---|---|---|---|---|
| Jan | 75% | 82% | 2.1 | 10:10 |
| Feb | 74% | 79% | 2.9 | 10:57 |
| Mar | 73% | 77% | 3.9 | 11:53 |
| Apr | 76% | 74% | 4.8 | 12:58 |
| May | 79% | 75% | 5.2 | 13:53 |
| Jun | 84% | 83% | 4.6 | 14:21 |
| Jul | 86% | 74% | 4.9 | 14:10 |
| Aug | 83% | 66% | 5.2 | 13:23 |
| Sep | 81% | 71% | 4.2 | 12:20 |
| Oct | 76% | 67% | 3.5 | 11:17 |
| Nov | 74% | 72% | 2.5 | 10:23 |
| Dec | 75% | 80% | 1.9 | 9:57 |
Humid. = average relative humidity at 2 m; cloud = average cloud amount; solar = average daily solar energy reaching the ground in kWh/m² (all-sky); daylight in hours:minutes, calculated for the 15th of each month.
What the climate of Karatsu is like
The warmest month is August, with an average high of 30 °C86 °F and a low of 25 °C77 °F. The coldest is January, when highs average 10 °C49 °F and lows 5 °C42 °F. Seasons are strongly marked: the warmest month is on average 20 °C36.1 °F warmer than the coldest.
It is wet, with about 1,963 mm77 in of precipitation per year. The wettest three-month stretch is June–August, which brings 44% of the annual total. The wettest month is July (347 mm14 in), the driest is January (69 mm2.7 in).
Relative humidity ranges from 73% in March to 86% in July. The clearest skies (lowest average cloud amount, 66%) are typical of August. Average wind speed near the ground ranges from 9 km/h (6 mph) in June to 15 km/h (9 mph) in January. Daylight lasts from about 9.9 hours in December to 14.4 hours in June.
Best time to visit Karatsu
Based on these averages, the most comfortable months for sightseeing and outdoor activities are October: average highs of 22 °C72 °F to 22 °C72 °F with 111 mm4.4 in to 111 mm4.4 in of precipitation per month.
The most challenging month is July, which is very wet (347 mm14 in) and humid (86% relative humidity).
Comfort score: months are ranked by how close they come to an average high of 21–28 °C (70–82 °F), lows above 5 °C (41 °F), little precipitation and moderate humidity. The best-ranked months of each place are recommended, even where none meets all of these. These are general rules of thumb applied to long-term averages.
What to pack for Karatsu
- Winter (December–February) — highs 1049 to 12 °C53 °F, lows 542 to 8 °C46 °F, about 80 mm3.2 in of precipitation a month. Pack a warm coat, layers and closed shoes.
- Spring (March–May) — highs 1356 to 22 °C71 °F, lows 847 to 16 °C60 °F, about 152 mm6.0 in of precipitation a month. Pack long sleeves, a sweater and a medium jacket and an umbrella or light rain jacket.
- Summer (June–August) — highs 2577 to 30 °C86 °F, lows 2067 to 25 °C77 °F, about 288 mm11 in of precipitation a month. Pack light summer clothes such as T-shirts, shorts or light dresses and a good rain jacket or umbrella and quick-drying shoes.
- Autumn (September–November) — highs 1763 to 27 °C80 °F, lows 1355 to 22 °C72 °F, about 134 mm5.3 in of precipitation a month. Pack light layers — T-shirts plus a light sweater or jacket and an umbrella or light rain jacket.
How Karatsu compares
Compared with Sasebo, about 38 km to the southwest, Karatsu has practically the same average temperature and receives 6% less precipitation (1,963 mm77 in vs 2,078 mm82 in). The difference is largest in December (1.1 °C1.9 °F warmer).
Of the 111 places in Japan covered by World Climates, Karatsu is the 15th warmest by annual mean temperature and the 21st wettest by annual precipitation. See all of them on the Japan climate page.
Places in other countries with the most similar temperature and rainfall pattern: Jeju City (South Korea, Cfa), Zhoushan (China, Cfa) and Gijang (South Korea, Cfa).
Nearby places
- Sasebo 38 km · 17 °C62 °F · 2,078 mm82 in
- Saga 39 km · 17 °C62 °F · 2,078 mm82 in
- Fukuoka 45 km · 16 °C61 °F · 1,901 mm75 in
- Ōmuta 64 km · 17 °C62 °F · 2,130 mm84 in
- Isahaya 67 km · 16 °C61 °F · 2,078 mm82 in
- Nagasaki 77 km · 17 °C62 °F · 2,078 mm82 in
- Kitakyushu 93 km · 17 °C62 °F · 1,860 mm73 in
- Kumamoto 98 km · 17 °C62 °F · 2,130 mm84 in
Frequently asked questions
What is the warmest month in Karatsu?
August is the warmest month in Karatsu, with an average high of 30 °C (86 °F) and an average low of 25 °C (77 °F).
What is the coldest month in Karatsu?
January is the coldest month, with an average high of 10 °C (49 °F) and an average low of 5 °C (42 °F).
When does it rain the most in Karatsu?
July is the wettest month with about 347 mm (13.7 in) of precipitation; January is the driest with about 69 mm (2.7 in).
What is the best time to visit Karatsu?
Judging by long-term averages, the most comfortable months are October.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.
The grid cell’s average elevation is 62 m, while Karatsu lies at about 7 m. Temperatures on this page were therefore adjusted by +0.4 °C0.6 °F using the standard lapse rate of 6.5 °C per 1,000 m.