Isahaya climate — normals and trends
Isahaya (Japan) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 16.9 °C and it receives 2,088 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is August (26.8 °C on average) and the coldest is January (7.6 °C). Rainfall peaks in June.
Isahaya averages 0 frost days, 8 hot days (≥ 30 °C) and 149 rainy days per year.
Isahaya has warmed by +1.3 °C between 1940 and 2025, or +0.15 °C per decade. This trend is statistically significant.
The hottest day of the period reached 33.5 °C (on 21 August 2018) and the coldest -2.3 °C (on 16 February 1977).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
IsahayaNagasaki
- coords
- 32.84°, 130.04°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
16.9°C
Average daily high
18.8°C
Average daily low
15.1°C
Annual rainfall
2,088mm
Sunshine / day
8.2h
Mean relative humidity
76%
Average peak wind
21.6km/h
Seasonal range
19.2°C
Frost days (< 0 °C)
0 d/yr
Hot days (≥ 30 °C)
8 d/yr
Rainy days (≥ 1 mm)
149 d/yr
Annual snowfall
3.5 cm
Average feels-like high
18.7 °C
Average feels-like low
13.9 °C
Average peak gust
35.5 km/h
Tropical nights (≥ 20 °C)
111 d/yr
Solar radiation
14.4 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.3 °C
since 1940
+0.2 °C per decade · r² = 0.48 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
33.5 °C
21 August 2018
Coldest day
-2.3 °C
16 February 1977
Wettest day
180 mm
13 June 1945
Windiest day
90.4 km/h
27 September 1991
Strongest gust
168.1 km/h
27 September 1991
Hottest feels-like
40.4 °C
20 August 2013
Coldest feels-like
-9.8 °C
26 February 1981
Snowiest day
8.5 cm
18 January 1984
Sunniest day
13.6 h
12 June 1951
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 9.6 °C | +0.2 °C | 39 mm | -40 mm |
| Feb | 8.2 °C | -1.8 °C | 79 mm | -19 mm |
| Mar | 13.5 °C | +0.6 °C | 176 mm | +36 mm |
| Apr | 17.4 °C | +0.3 °C | 119 mm | -58 mm |
| May | 20.6 °C | 0.0 °C | 364 mm | +155 mm |
| Jun | 24.5 °C | +1.1 °C | 466 mm | +71 mm |
| Jul | 30.1 °C | +3.2 °C | 102 mm | -214 mm |
| Aug | 29.5 °C | +0.9 °C | 310 mm | +123 mm |
| Sep | 28.4 °C | +2.2 °C | 195 mm | -5 mm |
| Oct | 24.4 °C | +2.7 °C | 65 mm | -46 mm |
| Nov | 17.7 °C | +0.9 °C | 44 mm | -53 mm |
| Dec | 13.8 °C | +2.0 °C | 82 mm | -1 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of Isahaya?
Isahaya has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 16.9 °C and it receives 2,088 mm of precipitation per year.
What is the hottest day ever recorded in Isahaya?
The hottest day measured in Isahaya between 1940 and 2025 was 21 August 2018, reaching 33.5 °C.
What is the coldest day in Isahaya?
The coldest day measured in Isahaya between 1940 and 2025 was 16 February 1977, at -2.3 °C.
Does it snow in Isahaya?
Yes. Isahaya gets on average 3.5 cm of snow per year and has around 0 frost days.
Has the climate of Isahaya warmed?
Yes: Isahaya warmed by +1.3 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Isahaya?
The wettest day measured in Isahaya between 1940 and 2025 was 13 June 1945, with 180 mm of rain in 24 hours.
What was the windiest day in Isahaya?
The windiest day measured in Isahaya between 1940 and 2025 was 27 September 1991, with winds reaching 90.4 km/h.
What is the warmest month in Isahaya?
The warmest month in Isahaya is August (26.8 °C on average); the coldest is January (7.6 °C).
How much does it rain in Isahaya?
Isahaya receives on average 2,088 mm of precipitation per year, spread over about 149 rainy days.
Is it sunny in Isahaya?
Isahaya gets on average 8.2 hours of sunshine per day, roughly 2,993 hours per year over 1940-2025.
What is the biggest single-day snowfall in Isahaya?
The heaviest 24-hour snowfall measured in Isahaya between 1940 and 2025 was 18 January 1984, with 8.5 cm.
Are there tropical nights in Isahaya?
Yes: Isahaya has on average 111 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Isahaya?
In Isahaya, between 1940 and 2025, the highest apparent temperature reached 40.4 °C on 20 August 2013, and the lowest was -9.8 °C on 26 February 1981.
Compare Isahaya with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Isahaya