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Isahaya, Nagasaki Weather by Month and Climate Averages
Monthly normals · Rain · Snow
Sunshine · Freeze dates · Records · Best time to visit
What is the weather like in Isahaya, Nagasaki?
Isahaya, Nagasaki gets 1830 mm of precipitation a year over about 115 rainy days. August is the warmest month (average high 32°C) and January the coldest (average low 3°C).
Humid subtropical climate
Isahaya, Nagasaki has hot summers and chilly winters. Daytime highs range from about 11°C in January to 32°C in August. June 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 | 4° | 12° |
| Spring | Mar–May | 11° | 19° |
| Summer | Jun–Aug | 23° | 29° |
| Autumn | Sep–Nov | 16° | 24° |
How much rain does Isahaya get?
Isahaya gets 1830 mm of precipitation in an average year, spread over about 115 days with measurable rain. That is more rainy days than 51% of Japan.
June is the wettest month, with 326 mm. January is the driest, with 59 mm. June has the most rainy days, about 14.
The longest dry spell in the last five years lasted 21 days, to November 12, 2022.
From October 2025 to September 2026 Isahaya got 5414 mm of rain, against a normal of 1830 mm for those months. August 2026 had the most, with 2065 mm.
Isahaya weather by month
Isahaya weather in January
In January, Isahaya averages a high of 11°C and a low of 3°C. It gets 59 mm of precipitation over about 10 rainy days. Estimated sunshine is 39% of daylight hours, derived from ERA5 cloud cover. The January record high is 21°C (2002) and the record low is -4°C (1970).
Isahaya weather in February
In February, Isahaya averages a high of 12°C and a low of 4°C. It gets 76 mm of precipitation over about 9 rainy days. Estimated sunshine is 39% of daylight hours, derived from ERA5 cloud cover. The February record high is 23°C (2010) and the record low is -4°C (1977).
Isahaya weather in March
In March, Isahaya averages a high of 16°C and a low of 7°C. It gets 113 mm of precipitation over about 10 rainy days. Estimated sunshine is 38% of daylight hours, derived from ERA5 cloud cover. The March record high is 24°C (2007) and the record low is -3°C (1977).
Isahaya weather in April
In April, Isahaya averages a high of 20°C and a low of 11°C. It gets 145 mm of precipitation over about 9 rainy days. Estimated sunshine is 38% of daylight hours, derived from ERA5 cloud cover. The April record high is 29°C (1998) and the record low is 1°C (1972). April is one of the most comfortable months to visit.
Isahaya weather in May
In May, Isahaya averages a high of 24°C and a low of 16°C. It gets 162 mm of precipitation over about 10 rainy days. Estimated sunshine is 33% of daylight hours, derived from ERA5 cloud cover. The May record high is 32°C (1998) and the record low is 4°C (2026). May is one of the most comfortable months to visit.
Isahaya weather in June
In June, Isahaya averages a high of 26°C and a low of 20°C. It gets 326 mm of precipitation over about 14 rainy days. Estimated sunshine is 22% of daylight hours, derived from ERA5 cloud cover. The June record high is 37°C (2004) and the record low is 13°C (1981).
Isahaya weather in July
In July, Isahaya averages a high of 31°C and a low of 24°C. It gets 288 mm of precipitation over about 12 rainy days. Estimated sunshine is 26% of daylight hours, derived from ERA5 cloud cover. The July record high is 38°C (1994) and the record low is 15°C (2026).
Isahaya weather in August
In August, Isahaya averages a high of 32°C and a low of 25°C. It gets 204 mm of precipitation over about 10 rainy days. Estimated sunshine is 44% of daylight hours, derived from ERA5 cloud cover. The August record high is 38°C (2026) and the record low is 19°C (1979).
Isahaya weather in September
In September, Isahaya averages a high of 29°C and a low of 22°C. It gets 186 mm of precipitation over about 9 rainy days. Estimated sunshine is 43% of daylight hours, derived from ERA5 cloud cover. The September record high is 37°C (2026) and the record low is 12°C (1973).
Isahaya weather in October
In October, Isahaya averages a high of 24°C and a low of 16°C. It gets 102 mm of precipitation over about 6 rainy days. Estimated sunshine is 56% of daylight hours, derived from ERA5 cloud cover. The October record high is 32°C (2026) and the record low is 5°C (1970). October is one of the most comfortable months to visit.
Isahaya weather in November
In November, Isahaya averages a high of 18°C and a low of 11°C. It gets 96 mm of precipitation over about 8 rainy days. Estimated sunshine is 51% of daylight hours, derived from ERA5 cloud cover. The November record high is 26°C (1979) and the record low is 1°C (1970). November is one of the most comfortable months to visit.
Isahaya weather in December
In December, Isahaya averages a high of 13°C and a low of 6°C. It gets 73 mm of precipitation over about 9 rainy days. Estimated sunshine is 41% of daylight hours, derived from ERA5 cloud cover. The December record high is 23°C (2018) and the record low is -2°C (1973).
Sunshine, humidity and wind in Isahaya
October is the sunniest month in Isahaya, with estimated sunshine of 56% of daylight hours from ERA5 cloud cover. June is the cloudiest, at 22%. The annual cloud-cover estimate is 39% of daylight hours; it is not a measurement of sunshine duration. Isahaya is sunnier than 60% of Japan.
Humidity peaks in July at 88% and is lowest in December at 66%.
Isahaya has about 22 days a year above 32°C. Isahaya is hotter than 58% of Japan.
Isahaya weather records
These records cover NAGASAKI during 1970–2026. Earlier records or other stations in the city may differ.
The hottest temperature on record at the Isahaya station is 38°C, on July 23, 1994. The coldest is -4°C, on January 25, 2016.
The wettest day in the available station history brought 852 mm of precipitation, on July 17, 2026.
41 all-time records have been set at the station since 1970.
The best time to visit Isahaya
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 4°C.
Spring (March–May) is mild, with average highs around 20°C and lows near 11°C.
Summer (June–August) is hot, with average highs around 30°C and lows near 23°C. It can feel humid.
Autumn (September–November) is warm, with average highs around 24°C and lows near 16°C.
Monthly climate
| Month | Average low | Average high | Precip | Rain days | Humidity | Estimated sunshine | Record high | Record low |
|---|---|---|---|---|---|---|---|---|
| January | 3° | 11° | 59 mm | 10 | 68% | 39% | 21° | -4° |
| February | 4° | 12° | 76 mm | 9 | 69% | 39% | 23° | -4° |
| March | 7° | 16° | 113 mm | 10 | 72% | 38% | 24° | -3° |
| April | 11° | 20° | 145 mm | 9 | 72% | 38% | 29° | 1° |
| May | 16° | 24° | 162 mm | 10 | 79% | 33% | 32° | 4° |
| June | 20° | 26° | 326 mm | 14 | 86% | 22% | 37° | 13° |
| July | 24° | 31° | 288 mm | 12 | 88% | 26% | 38° | 15° |
| August | 25° | 32° | 204 mm | 10 | 83% | 44% | 38° | 19° |
| September | 22° | 29° | 186 mm | 9 | 79% | 43% | 37° | 12° |
| October | 16° | 24° | 102 mm | 6 | 70% | 56% | 32° | 5° |
| November | 11° | 18° | 96 mm | 8 | 69% | 51% | 26° | 1° |
| December | 6° | 13° | 73 mm | 9 | 66% | 41% | 23° | -2° |
Station: NAGASAKI, 21 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.
Isahaya climate questions
How much rain does Isahaya get?
Isahaya gets 1830 mm of precipitation in an average year, over about 115 rainy days.
What is the wettest month in Isahaya?
June is the wettest month in Isahaya, with 326 mm. January is the driest, with 59 mm.
How many rainy days does Isahaya have a year?
Isahaya has about 115 days with measurable rain in an average year. June has the most, about 14.
What is the hottest month in Isahaya?
August is the warmest month in Isahaya, with an average high of 32°C.
What is the coldest month in Isahaya?
January is the coldest month in Isahaya, with an average low of 3°C.
What is the record high temperature in Isahaya?
Within the available 1970–2026 station history, the record high at the Isahaya station is 38°C, set on July 23, 1994. The record low is -4°C, on January 25, 2016.
What is the sunniest month in Isahaya?
October is the sunniest month in Isahaya, with estimated sunshine of 56% of daylight hours from ERA5 cloud cover. June is the cloudiest.
What is the best time to visit Isahaya?
The most comfortable time to visit is typically April to May and October to November, when daytime highs sit near 22°C.