Saikai climate — normals and trends
Saikai (Japan) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 16.9 °C and it receives 1,899 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 (27.0 °C on average) and the coldest is January (7.4 °C). Rainfall peaks in June.
Saikai averages 0 frost days, 8 hot days (≥ 30 °C) and 141 rainy days per year.
Saikai has warmed by +1.6 °C between 1940 and 2025, or +0.19 °C per decade. This trend is statistically significant.
The hottest day of the period reached 33.3 °C (on 20 August 2013) 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
SaikaiNagasaki
- coords
- 32.98°, 129.68°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
16.9°C
Average daily high
18.6°C
Average daily low
15.3°C
Annual rainfall
1,899mm
Sunshine / day
8.2h
Mean relative humidity
75%
Average peak wind
21.0km/h
Seasonal range
19.6°C
Frost days (< 0 °C)
0 d/yr
Hot days (≥ 30 °C)
8 d/yr
Rainy days (≥ 1 mm)
141 d/yr
Annual snowfall
3.2 cm
Average feels-like high
18.6 °C
Average feels-like low
14.2 °C
Average peak gust
36.4 km/h
Tropical nights (≥ 20 °C)
115 d/yr
Solar radiation
14.3 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.6 °C
since 1940
+0.2 °C per decade · r² = 0.58 · 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
33.3 °C
20 August 2013
Coldest day
-2.3 °C
16 February 1977
Wettest day
199 mm
2 June 1988
Windiest day
89.9 km/h
31 August 1987
Strongest gust
190.8 km/h
31 August 1987
Hottest feels-like
41.1 °C
5 August 2023
Coldest feels-like
-10.5 °C
26 February 1981
Snowiest day
12.7 cm
15 February 1968
Sunniest day
13.6 h
18 June 1958
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 | +0.5 °C | 35 mm | -34 mm |
| Feb | 7.9 °C | -1.7 °C | 73 mm | -14 mm |
| Mar | 13.1 °C | +0.5 °C | 167 mm | +42 mm |
| Apr | 17.3 °C | +0.5 °C | 102 mm | -64 mm |
| May | 20.4 °C | 0.0 °C | 343 mm | +153 mm |
| Jun | 24.4 °C | +1.0 °C | 454 mm | +111 mm |
| Jul | 30.0 °C | +3.1 °C | 113 mm | -175 mm |
| Aug | 29.6 °C | +1.1 °C | 275 mm | +96 mm |
| Sep | 28.5 °C | +2.4 °C | 202 mm | +15 mm |
| Oct | 24.4 °C | +2.8 °C | 59 mm | -44 mm |
| Nov | 17.7 °C | +1.0 °C | 54 mm | -36 mm |
| Dec | 13.6 °C | +1.9 °C | 70 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 Saikai?
Saikai has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 16.9 °C and it receives 1,899 mm of precipitation per year.
What is the hottest day ever recorded in Saikai?
The hottest day measured in Saikai between 1940 and 2025 was 20 August 2013, reaching 33.3 °C.
What is the coldest day in Saikai?
The coldest day measured in Saikai between 1940 and 2025 was 16 February 1977, at -2.3 °C.
Does it snow in Saikai?
Yes. Saikai gets on average 3.2 cm of snow per year and has around 0 frost days.
Has the climate of Saikai warmed?
Yes: Saikai warmed by +1.6 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Saikai?
The wettest day measured in Saikai between 1940 and 2025 was 2 June 1988, with 199 mm of rain in 24 hours.
What was the windiest day in Saikai?
The windiest day measured in Saikai between 1940 and 2025 was 31 August 1987, with winds reaching 89.9 km/h.
What is the warmest month in Saikai?
The warmest month in Saikai is August (27.0 °C on average); the coldest is January (7.4 °C).
How much does it rain in Saikai?
Saikai receives on average 1,899 mm of precipitation per year, spread over about 141 rainy days.
Is it sunny in Saikai?
Saikai 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 Saikai?
The heaviest 24-hour snowfall measured in Saikai between 1940 and 2025 was 15 February 1968, with 12.7 cm.
Are there tropical nights in Saikai?
Yes: Saikai has on average 115 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Saikai?
In Saikai, between 1940 and 2025, the highest apparent temperature reached 41.1 °C on 5 August 2023, and the lowest was -10.5 °C on 26 February 1981.
Compare Saikai with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Saikai