Iruma climate — normals and trends

Q: What is the climate of Iruma?

Iruma has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 12.8 °C and it receives 1,894 mm of precipitation per year.

Q: What is the hottest day ever recorded in Iruma?

The hottest day measured in Iruma between 1940 and 2025 was 15 August 1996, reaching 36.7 °C.

Q: What is the coldest day in Iruma?

The coldest day measured in Iruma between 1940 and 2025 was 6 February 1952, at -19.1 °C.

Q: Does it snow in Iruma?

Yes. Iruma gets on average 66.2 cm of snow per year and has around 75 frost days.

Q: Has the climate of Iruma warmed?

Yes: Iruma warmed by +2.7 °C between 1940 and 2025, a statistically significant trend.

Q: What is the wettest day in Iruma?

The wettest day measured in Iruma between 1940 and 2025 was 26 September 1958, with 261 mm of rain in 24 hours.

Q: What was the windiest day in Iruma?

The windiest day measured in Iruma between 1940 and 2025 was 26 September 1959, with winds reaching 56.7 km/h.

Q: What is the warmest month in Iruma?

The warmest month in Iruma is August (24.5 °C on average); the coldest is January (1.2 °C).

Q: How much does it rain in Iruma?

Iruma receives on average 1,894 mm of precipitation per year, spread over about 185 rainy days.

Q: Is it sunny in Iruma?

Iruma gets on average 8.2 hours of sunshine per day, roughly 2,993 hours per year over 1940-2025.

Iruma (Japan) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 12.8 °C and it receives 1,894 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 (24.5 °C on average) and the coldest is January (1.2 °C). Rainfall peaks in September.

Iruma averages 75 frost days, 16 hot days (≥ 30 °C) and 185 rainy days per year.

Iruma has warmed by +2.7 °C between 1940 and 2025, or +0.31 °C per decade. This trend is statistically significant.

The number of frost days there went from about 96 to 54 per year over the period.

The hottest day of the period reached 36.7 °C (on 15 August 1996) and the coldest -19.1 °C (on 6 February 1952).

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

IrumaSaitama

coords: 35.82°, 139.37°
period: 1940–2025 · 86 yrs

CfaHumid subtropicalWarmest monthAugustColdest monthJanuaryWettest monthSeptemberDriest monthJanuary

Mean daily temperature

12.8°C

Average daily high

16.9°C

Average daily low

9.1°C

Annual rainfall

1,894mm

Sunshine / day

8.2h

Mean relative humidity

76%

Average peak wind

11.4km/h

Seasonal range

23.3°C

Frost days (< 0 °C)

75 d/yr

Hot days (≥ 30 °C)

16 d/yr

Rainy days (≥ 1 mm)

185 d/yr

Annual snowfall

66.2 cm

Average feels-like high

16.6 °C

Average feels-like low

8.1 °C

Average peak gust

30.4 km/h

Tropical nights (≥ 20 °C)

56 d/yr

Solar radiation

13.5 MJ/m²

Has the climate changed?

One stripe per year, 1940 to 2025

+2.7 °C

since 1940

+0.3 °C per decade · r² = 0.68 · p = < 0.001

19402025

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

36.7 °C

15 August 1996

Coldest day

-19.1 °C

6 February 1952

Wettest day

261 mm

26 September 1958

Windiest day

56.7 km/h

26 September 1959

Strongest gust

177.5 km/h

27 September 1959

Hottest feels-like

42.8 °C

5 August 2025

Coldest feels-like

-24.1 °C

6 February 1952

Snowiest day

49.0 cm

23 March 1986

Sunniest day

14.0 h

23 June 1940

Year	Hottest day	Coldest day	Annual mean	Rainfall	Hot days	Frost days
2025	35.6 °C5 August 2025	-5.4 °C23 February 2025	14.6 °C	1,422 mm	61	68
2024	34.6 °C7 July 2024	-3.9 °C7 February 2024	15.1 °C	2,167 mm	55	59
2023	34.7 °C12 July 2023	-6.6 °C26 January 2023	15.2 °C	1,626 mm	51	44
2022	35.1 °C25 June 2022	-5.8 °C12 February 2022	14.1 °C	1,890 mm	33	70
2021	35.3 °C10 August 2021	-5.0 °C9 January 2021	14.2 °C	2,034 mm	23	47
2020	35.8 °C11 August 2020	-4.3 °C7 February 2020	14.3 °C	1,963 mm	29	44
2019	34.5 °C9 September 2019	-3.7 °C4 January 2019	14.2 °C	2,107 mm	27	48
2018	34.9 °C23 July 2018	-12.8 °C25 January 2018	14.6 °C	1,794 mm	43	51
2017	32.6 °C9 August 2017	-5.1 °C25 January 2017	13.5 °C	1,909 mm	24	70
2016	34.0 °C9 August 2016	-9.5 °C21 January 2016	14.0 °C	1,939 mm	13	57
2015	33.9 °C13 July 2015	-6.0 °C18 January 2015	14.0 °C	1,982 mm	24	58
2014	34.1 °C5 August 2014	-8.6 °C5 February 2014	13.3 °C	1,877 mm	20	82
2013	34.2 °C10 August 2013	-11.7 °C18 January 2013	13.6 °C	1,714 mm	26	71
2012	32.4 °C16 July 2012	-8.5 °C27 January 2012	12.9 °C	1,977 mm	20	83
2011	33.9 °C18 August 2011	-6.9 °C16 February 2011	13.4 °C	1,989 mm	28	80
2010	32.9 °C23 July 2010	-4.9 °C11 March 2010	13.7 °C	2,255 mm	41	58
2009	33.4 °C15 July 2009	-10.1 °C25 January 2009	13.7 °C	2,033 mm	7	39
2008	32.1 °C8 August 2008	-7.7 °C4 February 2008	13.4 °C	2,002 mm	13	65
2007	33.8 °C16 August 2007	-3.7 °C25 February 2007	13.8 °C	1,920 mm	27	40
2006	32.7 °C14 July 2006	-5.5 °C23 January 2006	13.6 °C	1,975 mm	11	49
2005	32.8 °C27 July 2005	-9.8 °C2 January 2005	13.2 °C	1,825 mm	19	83
2004	34.5 °C20 July 2004	-8.4 °C23 January 2004	14.2 °C	2,029 mm	26	50
2003	32.5 °C23 August 2003	-10.9 °C30 January 2003	12.8 °C	2,088 mm	12	67
2002	33.7 °C8 August 2002	-8.2 °C28 December 2002	13.3 °C	1,826 mm	28	58
2001	34.5 °C13 July 2001	-11.1 °C15 January 2001	13.0 °C	1,898 mm	19	79
2000	34.5 °C2 September 2000	-9.0 °C28 January 2000	13.6 °C	1,831 mm	18	56
1999	33.4 °C30 July 1999	-11.2 °C14 February 1999	13.8 °C	1,765 mm	24	59
1998	33.8 °C16 August 1998	-12.5 °C25 January 1998	13.7 °C	2,301 mm	14	63
1997	34.8 °C5 July 1997	-7.9 °C22 February 1997	13.3 °C	1,543 mm	17	61
1996	36.7 °C15 August 1996	-12.3 °C20 February 1996	12.4 °C	1,758 mm	15	79
1995	33.1 °C24 July 1995	-8.6 °C6 March 1995	12.9 °C	1,666 mm	30	83
1994	33.8 °C2 August 1994	-14.5 °C31 January 1994	13.5 °C	1,766 mm	27	72
1993	31.0 °C28 July 1993	-7.6 °C22 January 1993	12.4 °C	2,196 mm	6	65
1992	33.1 °C3 September 1992	-9.9 °C2 February 1992	12.9 °C	1,818 mm	17	67
1991	34.5 °C24 July 1991	-15.2 °C30 December 1991	13.4 °C	2,251 mm	18	62
1990	34.4 °C17 July 1990	-14.2 °C28 January 1990	13.9 °C	1,954 mm	24	49
1989	31.4 °C7 August 1989	-11.1 °C29 January 1989	13.1 °C	2,030 mm	4	45
1988	32.1 °C9 July 1988	-9.1 °C19 February 1988	12.2 °C	2,025 mm	4	70
1987	34.8 °C24 July 1987	-10.1 °C15 January 1987	13.0 °C	1,665 mm	26	75
1986	31.7 °C4 September 1986	-13.5 °C26 February 1986	11.9 °C	1,951 mm	7	80
1985	32.0 °C18 July 1985	-14.3 °C31 January 1985	12.4 °C	1,968 mm	13	79
1984	33.8 °C3 September 1984	-15.8 °C9 February 1984	11.4 °C	1,352 mm	15	103
1983	33.6 °C19 August 1983	-11.8 °C22 February 1983	12.4 °C	1,885 mm	13	83
1982	30.7 °C22 August 1982	-11.9 °C7 February 1982	12.7 °C	2,099 mm	3	65
1981	31.7 °C10 July 1981	-14.5 °C28 February 1981	11.8 °C	1,830 mm	8	86
1980	31.9 °C23 July 1980	-10.9 °C7 February 1980	12.0 °C	2,026 mm	1	90
1979	32.3 °C23 June 1979	-15.9 °C16 January 1979	13.4 °C	2,185 mm	18	63
1978	34.1 °C21 August 1978	-12.6 °C19 February 1978	12.7 °C	1,602 mm	29	85
1977	32.6 °C13 July 1977	-13.2 °C17 February 1977	12.6 °C	2,039 mm	4	71
1976	31.7 °C24 August 1976	-11.2 °C21 March 1976	12.1 °C	1,965 mm	8	77
1975	32.5 °C5 August 1975	-12.5 °C16 February 1975	12.4 °C	2,046 mm	15	93
1974	31.8 °C30 July 1974	-14.7 °C12 February 1974	12.1 °C	2,070 mm	7	83
1973	32.5 °C2 September 1973	-7.0 °C14 January 1973	12.7 °C	1,749 mm	21	88
1972	33.3 °C19 August 1972	-9.8 °C9 February 1972	13.0 °C	2,419 mm	17	71
1971	33.1 °C8 July 1971	-12.6 °C6 January 1971	12.3 °C	2,174 mm	15	71
1970	32.5 °C18 July 1970	-14.3 °C6 January 1970	12.0 °C	1,890 mm	17	91
1969	33.7 °C30 July 1969	-12.3 °C16 January 1969	12.3 °C	1,937 mm	11	86
1968	31.9 °C20 July 1968	-13.7 °C2 February 1968	12.3 °C	2,136 mm	6	73
1967	32.1 °C11 August 1967	-16.6 °C14 February 1967	12.3 °C	1,767 mm	17	90
1966	30.4 °C17 July 1966	-10.8 °C29 December 1966	11.8 °C	2,070 mm	4	91
1965	31.6 °C30 July 1965	-13.2 °C4 February 1965	11.5 °C	2,012 mm	3	98
1964	32.4 °C16 August 1964	-10.3 °C14 February 1964	12.7 °C	2,189 mm	20	74
1963	32.9 °C26 June 1963	-9.0 °C19 February 1963	12.4 °C	1,686 mm	17	91
1962	35.1 °C4 August 1962	-8.7 °C26 January 1962	12.6 °C	1,790 mm	26	95
1961	34.2 °C26 July 1961	-8.3 °C2 February 1961	13.5 °C	1,834 mm	20	84
1960	31.0 °C5 August 1960	-9.8 °C25 January 1960	12.8 °C	1,958 mm	19	69
1959	32.9 °C2 September 1959	-11.3 °C7 January 1959	13.0 °C	2,434 mm	15	69
1958	33.7 °C1 August 1958	-14.7 °C31 March 1958	12.7 °C	2,104 mm	12	76
1957	32.2 °C23 August 1957	-12.0 °C12 February 1957	12.4 °C	2,003 mm	14	80
1956	32.4 °C2 August 1956	-11.3 °C26 January 1956	12.2 °C	1,958 mm	9	95
1955	32.9 °C25 July 1955	-8.8 °C12 February 1955	13.2 °C	1,683 mm	15	72
1954	32.3 °C9 August 1954	-14.3 °C30 January 1954	12.4 °C	1,837 mm	9	66
1953	34.2 °C21 August 1953	-13.2 °C23 February 1953	12.3 °C	2,060 mm	9	74
1952	31.2 °C4 September 1952	-19.1 °C6 February 1952	11.1 °C	1,750 mm	4	106
1951	31.4 °C10 August 1951	-15.3 °C15 January 1951	11.6 °C	1,846 mm	2	90
1950	30.9 °C9 July 1950	-11.6 °C21 February 1950	11.9 °C	1,610 mm	6	101
1949	30.7 °C18 July 1949	-9.4 °C30 December 1949	11.7 °C	1,985 mm	2	94
1948	29.5 °C9 September 1948	-7.3 °C7 February 1948	12.3 °C	1,859 mm	0	82
1947	31.6 °C15 August 1947	-12.2 °C4 February 1947	10.8 °C	1,599 mm	14	109
1946	32.5 °C16 July 1946	-13.3 °C4 February 1946	11.8 °C	1,560 mm	8	104
1945	29.8 °C9 September 1945	-18.0 °C24 February 1945	11.1 °C	2,006 mm	0	105
1944	31.2 °C1 July 1944	-7.3 °C20 February 1944	12.0 °C	1,532 mm	3	101
1943	29.5 °C9 August 1943	-10.2 °C16 February 1943	11.4 °C	1,071 mm	0	97
1942	31.3 °C17 August 1942	-16.5 °C14 February 1942	11.6 °C	1,285 mm	4	95
1941	30.1 °C28 July 1941	-14.1 °C26 January 1941	11.4 °C	1,998 mm	2	97
1940	32.2 °C25 July 1940	-13.4 °C19 February 1940	11.3 °C	1,246 mm	9	98

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?

Year

Across the whole year

Average daily high

19.3 °C

+2.4 °C

Hot days (≥ 30 °C)

61 d/yr

+45

Frost days (< 0 °C)

68 d/yr

-7

Annual rainfall

1422 mm

-472 mm

Month by month

	High	vs. normal	Precipitation	vs. normal
Jan	8.8 °C	+2.4 °C	48 mm	-13 mm
Feb	8.7 °C	+1.8 °C	23 mm	-53 mm
Mar	13.1 °C	+2.7 °C	178 mm	+50 mm
Apr	18.3 °C	+2.3 °C	153 mm	+13 mm
May	20.8 °C	+0.5 °C	206 mm	+40 mm
Jun	26.6 °C	+3.8 °C	145 mm	-85 mm
Jul	30.5 °C	+3.8 °C	132 mm	-107 mm
Aug	31.6 °C	+3.6 °C	102 mm	-123 mm
Sep	27.7 °C	+3.6 °C	194 mm	-55 mm
Oct	19.3 °C	+0.7 °C	148 mm	-66 mm
Nov	14.7 °C	+0.9 °C	29 mm	-77 mm
Dec	10.5 °C	+1.5 °C	64 mm	+3 mm

The year's extremes

Hottest day

35.6 °C

5 Aug 2025

Coldest day

-5.4 °C

23 Feb 2025

Wettest day

53.4 mm

2 May 2025

Windiest day

24.9 km/h

15 Jul 2025

Strongest gust

63.7 km/h

13 Feb 2025

Hottest feels-like

42.8 °C

5 Aug 2025

Coldest feels-like

-9.7 °C

23 Feb 2025

Snowiest day

13.9 cm

19 Mar 2025

Sunniest day

14.0 h

28 Jun 2025

What was the weather like that day?

Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.

Date

Frequently asked questions

What is the climate of Iruma?

Iruma has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 12.8 °C and it receives 1,894 mm of precipitation per year.

What is the hottest day ever recorded in Iruma?

The hottest day measured in Iruma between 1940 and 2025 was 15 August 1996, reaching 36.7 °C.

What is the coldest day in Iruma?

The coldest day measured in Iruma between 1940 and 2025 was 6 February 1952, at -19.1 °C.

Does it snow in Iruma?

Yes. Iruma gets on average 66.2 cm of snow per year and has around 75 frost days.

Has the climate of Iruma warmed?

Yes: Iruma warmed by +2.7 °C between 1940 and 2025, a statistically significant trend.

What is the wettest day in Iruma?

The wettest day measured in Iruma between 1940 and 2025 was 26 September 1958, with 261 mm of rain in 24 hours.

What was the windiest day in Iruma?

The windiest day measured in Iruma between 1940 and 2025 was 26 September 1959, with winds reaching 56.7 km/h.

What is the warmest month in Iruma?

The warmest month in Iruma is August (24.5 °C on average); the coldest is January (1.2 °C).

How much does it rain in Iruma?

Iruma receives on average 1,894 mm of precipitation per year, spread over about 185 rainy days.

Is it sunny in Iruma?

Iruma 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 Iruma?

The heaviest 24-hour snowfall measured in Iruma between 1940 and 2025 was 23 March 1986, with 49.0 cm.

Are there tropical nights in Iruma?

Yes: Iruma has on average 56 tropical nights per year (temperature staying above 20 °C), over 1940-2025.

What was the most extreme apparent temperature in Iruma?

In Iruma, between 1940 and 2025, the highest apparent temperature reached 42.8 °C on 5 August 2025, and the lowest was -24.1 °C on 6 February 1952.

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