Portsmouth climate — normals and trends

Q: What is the climate of Portsmouth?

Portsmouth has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 12.7 °C and it receives 1,078 mm of precipitation per year.

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

The hottest day measured in Portsmouth between 1940 and 2025 was 14 July 1954, reaching 41.1 °C.

Q: What is the coldest day in Portsmouth?

The coldest day measured in Portsmouth between 1940 and 2025 was 21 January 1984, at -28.5 °C.

Q: Does it snow in Portsmouth?

Yes. Portsmouth gets on average 41.9 cm of snow per year and has around 82 frost days.

Q: Has the climate of Portsmouth warmed?

Yes: Portsmouth warmed by +1.6 °C between 1940 and 2025, a statistically significant trend.

Q: What is the wettest day in Portsmouth?

The wettest day measured in Portsmouth between 1940 and 2025 was 17 September 2004, with 135 mm of rain in 24 hours.

Q: What was the windiest day in Portsmouth?

The windiest day measured in Portsmouth between 1940 and 2025 was 27 September 2024, with winds reaching 40.9 km/h.

Q: What is the warmest month in Portsmouth?

The warmest month in Portsmouth is July (24.3 °C on average); the coldest is January (0.2 °C).

Q: How much does it rain in Portsmouth?

Portsmouth receives on average 1,078 mm of precipitation per year, spread over about 131 rainy days.

Q: Is it sunny in Portsmouth?

Portsmouth gets on average 8.7 hours of sunshine per day, roughly 3,175 hours per year over 1940-2025.

Portsmouth (United States) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 12.7 °C and it receives 1,078 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 July (24.3 °C on average) and the coldest is January (0.2 °C). Rainfall peaks in May.

Portsmouth averages 82 frost days, 43 hot days (≥ 30 °C) and 131 rainy days per year.

Portsmouth has warmed by +1.6 °C between 1940 and 2025, or +0.19 °C per decade. This trend is statistically significant.

The number of frost days there went from about 93 to 71 per year over the period.

The hottest day of the period reached 41.1 °C (on 14 July 1954) and the coldest -28.5 °C (on 21 January 1984).

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

PortsmouthOhio

coords: 38.73°, -83.00°
period: 1940–2025 · 86 yrs

CfaHumid subtropicalWarmest monthJulyColdest monthJanuaryWettest monthMayDriest monthOctober

Mean daily temperature

12.7°C

Average daily high

18.0°C

Average daily low

8.1°C

Annual rainfall

1,078mm

Sunshine / day

8.7h

Mean relative humidity

70%

Average peak wind

14.4km/h

Seasonal range

24.1°C

Frost days (< 0 °C)

82 d/yr

Hot days (≥ 30 °C)

43 d/yr

Rainy days (≥ 1 mm)

131 d/yr

Annual snowfall

41.9 cm

Average feels-like high

17.0 °C

Average feels-like low

6.2 °C

Average peak gust

35.1 km/h

Tropical nights (≥ 20 °C)

42 d/yr

Solar radiation

14.9 MJ/m²

Has the climate changed?

One stripe per year, 1940 to 2025

+1.6 °C

since 1940

+0.2 °C per decade · r² = 0.36 · 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

41.1 °C

14 July 1954

Coldest day

-28.5 °C

21 January 1984

Wettest day

135 mm

17 September 2004

Windiest day

40.9 km/h

27 September 2024

Strongest gust

105.1 km/h

19 March 1948

Hottest feels-like

44.2 °C

14 July 1954

Coldest feels-like

-34.4 °C

17 January 1977

Snowiest day

30.2 cm

4 February 1998

Sunniest day

14.7 h

23 June 2025

Year	Hottest day	Coldest day	Annual mean	Rainfall	Hot days	Frost days
2025	34.1 °C19 August 2025	-24.0 °C22 January 2025	13.3 °C	1,256 mm	48	82
2024	36.9 °C28 August 2024	-13.3 °C21 January 2024	14.6 °C	1,156 mm	73	55
2023	35.1 °C24 August 2023	-9.0 °C4 February 2023	14.4 °C	951 mm	43	48
2022	36.7 °C22 June 2022	-19.9 °C23 December 2022	13.4 °C	1,216 mm	44	79
2021	34.3 °C29 June 2021	-10.4 °C17 February 2021	13.8 °C	1,215 mm	44	76
2020	35.4 °C4 July 2020	-9.7 °C26 December 2020	13.9 °C	1,280 mm	53	55
2019	36.8 °C13 September 2019	-19.2 °C21 January 2019	14.0 °C	1,398 mm	73	72
2018	34.3 °C14 July 2018	-17.3 °C2 January 2018	13.5 °C	1,480 mm	50	80
2017	34.4 °C18 June 2017	-12.8 °C7 January 2017	14.0 °C	1,279 mm	35	65
2016	34.4 °C25 July 2016	-16.4 °C24 January 2016	14.0 °C	1,130 mm	56	75
2015	33.8 °C11 June 2015	-26.1 °C20 February 2015	13.6 °C	1,142 mm	61	70
2014	35.4 °C13 July 2014	-20.8 °C24 January 2014	12.3 °C	1,060 mm	36	92
2013	33.7 °C10 September 2013	-12.6 °C22 January 2013	12.9 °C	1,096 mm	30	88
2012	38.7 °C7 July 2012	-9.0 °C12 February 2012	14.4 °C	967 mm	67	66
2011	38.1 °C3 September 2011	-15.4 °C22 January 2011	13.5 °C	1,460 mm	58	69
2010	36.1 °C4 August 2010	-15.7 °C8 February 2010	13.3 °C	920 mm	74	87
2009	32.8 °C16 August 2009	-20.3 °C5 February 2009	12.7 °C	1,076 mm	22	77
2008	35.6 °C21 July 2008	-15.6 °C22 December 2008	12.8 °C	1,117 mm	52	87
2007	37.5 °C16 August 2007	-18.9 °C15 February 2007	14.0 °C	840 mm	83	83
2006	36.0 °C2 August 2006	-13.8 °C19 February 2006	13.5 °C	1,089 mm	51	65
2005	37.3 °C12 August 2005	-14.8 °C24 January 2005	13.4 °C	931 mm	61	82
2004	32.9 °C6 July 2004	-22.0 °C31 January 2004	12.9 °C	1,394 mm	16	84
2003	32.7 °C27 August 2003	-20.7 °C27 January 2003	12.2 °C	1,332 mm	15	89
2002	36.3 °C5 August 2002	-12.4 °C4 March 2002	13.5 °C	1,178 mm	63	75
2001	33.3 °C9 August 2001	-15.1 °C21 January 2001	13.2 °C	943 mm	23	71
2000	32.5 °C9 August 2000	-20.5 °C27 January 2000	12.5 °C	1,074 mm	15	85
1999	36.7 °C30 July 1999	-16.0 °C5 January 1999	13.5 °C	913 mm	56	79
1998	34.9 °C6 September 1998	-12.1 °C1 January 1998	14.0 °C	1,084 mm	38	50
1997	35.0 °C27 July 1997	-16.4 °C17 January 1997	12.1 °C	1,034 mm	20	71
1996	32.9 °C30 June 1996	-22.3 °C4 February 1996	11.8 °C	1,451 mm	23	97
1995	35.7 °C15 July 1995	-23.0 °C12 February 1995	12.5 °C	1,065 mm	42	91
1994	36.1 °C20 June 1994	-28.3 °C19 January 1994	12.9 °C	1,156 mm	49	73
1993	37.3 °C28 July 1993	-16.8 °C15 March 1993	12.6 °C	1,112 mm	53	81
1992	35.3 °C10 July 1992	-16.7 °C16 January 1992	12.5 °C	841 mm	22	74
1991	37.0 °C2 August 1991	-14.5 °C16 February 1991	13.9 °C	965 mm	59	76
1990	35.4 °C9 July 1990	-11.4 °C26 February 1990	13.8 °C	1,422 mm	36	63
1989	35.3 °C11 July 1989	-26.6 °C22 December 1989	12.1 °C	1,285 mm	34	89
1988	39.2 °C8 July 1988	-16.2 °C6 January 1988	12.7 °C	901 mm	60	93
1987	36.8 °C24 July 1987	-12.3 °C27 January 1987	13.5 °C	846 mm	64	77
1986	36.4 °C25 July 1986	-17.1 °C12 February 1986	13.4 °C	998 mm	60	75
1985	35.7 °C8 September 1985	-25.6 °C20 January 1985	12.7 °C	1,144 mm	34	85
1984	34.3 °C2 September 1984	-28.5 °C21 January 1984	12.8 °C	1,209 mm	49	75
1983	38.6 °C20 August 1983	-22.2 °C25 December 1983	12.7 °C	1,167 mm	68	78
1982	33.9 °C26 July 1982	-24.5 °C17 January 1982	12.8 °C	1,026 mm	26	80
1981	33.5 °C25 July 1981	-18.4 °C12 February 1981	12.2 °C	972 mm	32	91
1980	37.7 °C16 July 1980	-21.2 °C3 March 1980	12.2 °C	984 mm	58	93
1979	32.7 °C8 August 1979	-23.7 °C10 February 1979	11.6 °C	1,378 mm	10	91
1978	38.0 °C27 June 1978	-19.9 °C11 February 1978	11.5 °C	1,224 mm	38	92
1977	36.1 °C17 July 1977	-28.4 °C17 January 1977	12.6 °C	1,147 mm	57	89
1976	34.8 °C15 July 1976	-20.5 °C9 January 1976	11.9 °C	815 mm	32	98
1975	34.4 °C1 August 1975	-12.3 °C10 February 1975	13.0 °C	1,213 mm	46	81
1974	33.0 °C14 July 1974	-11.2 °C12 January 1974	12.8 °C	1,151 mm	20	66
1973	34.8 °C2 September 1973	-14.7 °C17 February 1973	13.4 °C	1,228 mm	34	74
1972	34.7 °C23 July 1972	-22.8 °C16 January 1972	12.1 °C	1,116 mm	22	81
1971	35.8 °C28 June 1971	-16.9 °C2 February 1971	13.0 °C	830 mm	40	81
1970	35.9 °C1 July 1970	-20.6 °C21 January 1970	12.6 °C	1,025 mm	45	85
1969	36.4 °C5 July 1969	-15.4 °C5 January 1969	12.2 °C	829 mm	58	107
1968	35.0 °C24 August 1968	-22.5 °C8 January 1968	12.1 °C	902 mm	42	89
1967	34.9 °C15 June 1967	-17.2 °C25 February 1967	12.2 °C	972 mm	33	91
1966	35.5 °C27 June 1966	-19.9 °C30 January 1966	11.8 °C	1,029 mm	50	86
1965	35.7 °C24 July 1965	-17.5 °C5 February 1965	12.6 °C	814 mm	41	90
1964	36.2 °C3 August 1964	-15.4 °C14 January 1964	13.0 °C	903 mm	64	90
1963	34.4 °C3 August 1963	-26.1 °C28 January 1963	11.9 °C	746 mm	39	91
1962	37.3 °C20 August 1962	-19.2 °C10 January 1962	12.2 °C	1,034 mm	45	95
1961	32.9 °C13 September 1961	-23.5 °C25 January 1961	12.1 °C	1,144 mm	31	78
1960	35.6 °C8 September 1960	-18.2 °C22 December 1960	12.1 °C	927 mm	51	108
1959	36.5 °C13 August 1959	-20.1 °C5 January 1959	13.2 °C	968 mm	67	90
1958	33.7 °C4 July 1958	-19.6 °C17 February 1958	11.4 °C	1,026 mm	22	97
1957	36.1 °C21 July 1957	-20.4 °C17 January 1957	13.1 °C	1,129 mm	50	74
1956	34.2 °C5 August 1956	-13.8 °C27 January 1956	12.7 °C	1,237 mm	30	79
1955	35.6 °C3 August 1955	-19.4 °C13 February 1955	12.9 °C	903 mm	55	92
1954	41.1 °C14 July 1954	-15.5 °C13 January 1954	13.2 °C	847 mm	62	80
1953	37.7 °C31 August 1953	-14.0 °C18 December 1953	13.7 °C	810 mm	69	74
1952	38.5 °C23 July 1952	-13.2 °C30 January 1952	13.2 °C	884 mm	68	76
1951	34.8 °C22 July 1951	-27.4 °C3 February 1951	12.4 °C	1,191 mm	50	90
1950	32.1 °C24 June 1950	-15.5 °C18 December 1950	11.9 °C	1,407 mm	8	99
1949	36.2 °C4 July 1949	-12.9 °C30 January 1949	13.6 °C	1,026 mm	53	66
1948	36.3 °C28 August 1948	-22.7 °C25 January 1948	12.6 °C	1,267 mm	37	79
1947	32.5 °C5 August 1947	-15.7 °C8 February 1947	11.6 °C	842 mm	27	106
1946	32.9 °C19 July 1946	-11.7 °C22 January 1946	12.9 °C	1,095 mm	10	68
1945	34.6 °C1 September 1945	-19.8 °C3 February 1945	12.1 °C	1,094 mm	32	86
1944	35.1 °C11 August 1944	-16.4 °C22 December 1944	12.3 °C	1,010 mm	43	95
1943	34.1 °C1 September 1943	-20.3 °C8 March 1943	11.5 °C	843 mm	28	106
1942	34.7 °C2 August 1942	-21.7 °C8 January 1942	11.8 °C	1,138 mm	12	96
1941	33.6 °C11 August 1941	-14.6 °C18 March 1941	11.9 °C	928 mm	25	102
1940	35.6 °C29 July 1940	-23.4 °C27 January 1940	10.7 °C	1,076 mm	29	104

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

18.6 °C

+0.6 °C

Hot days (≥ 30 °C)

48 d/yr

Frost days (< 0 °C)

82 d/yr

Annual rainfall

1256 mm

+178 mm

Month by month

	High	vs. normal	Precipitation	vs. normal
Jan	1.2 °C	-3.3 °C	77 mm	-6 mm
Feb	8.3 °C	+1.6 °C	117 mm	+31 mm
Mar	16.9 °C	+4.7 °C	93 mm	-13 mm
Apr	20.2 °C	+1.8 °C	180 mm	+77 mm
May	21.6 °C	-1.5 °C	210 mm	+100 mm
Jun	28.8 °C	+1.2 °C	122 mm	+27 mm
Jul	30.3 °C	+0.7 °C	135 mm	+40 mm
Aug	28.8 °C	-0.3 °C	18 mm	-62 mm
Sep	27.7 °C	+2.0 °C	87 mm	+12 mm
Oct	20.0 °C	+0.5 °C	80 mm	+10 mm
Nov	12.3 °C	-0.1 °C	68 mm	-17 mm
Dec	6.8 °C	+0.1 °C	69 mm	-19 mm

The year's extremes

Hottest day

34.1 °C

19 Aug 2025

Coldest day

-24.0 °C

22 Jan 2025

Wettest day

47.4 mm

3 May 2025

Windiest day

34.1 km/h

15 Apr 2025

Strongest gust

81.0 km/h

19 Dec 2025

Hottest feels-like

40.0 °C

23 Jun 2025

Coldest feels-like

-29.4 °C

22 Jan 2025

Snowiest day

10.8 cm

5 Jan 2025

Sunniest day

14.7 h

23 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 Portsmouth?

Portsmouth has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 12.7 °C and it receives 1,078 mm of precipitation per year.

What is the hottest day ever recorded in Portsmouth?

The hottest day measured in Portsmouth between 1940 and 2025 was 14 July 1954, reaching 41.1 °C.

What is the coldest day in Portsmouth?

The coldest day measured in Portsmouth between 1940 and 2025 was 21 January 1984, at -28.5 °C.

Does it snow in Portsmouth?

Yes. Portsmouth gets on average 41.9 cm of snow per year and has around 82 frost days.

Has the climate of Portsmouth warmed?

Yes: Portsmouth warmed by +1.6 °C between 1940 and 2025, a statistically significant trend.

What is the wettest day in Portsmouth?

The wettest day measured in Portsmouth between 1940 and 2025 was 17 September 2004, with 135 mm of rain in 24 hours.

What was the windiest day in Portsmouth?

The windiest day measured in Portsmouth between 1940 and 2025 was 27 September 2024, with winds reaching 40.9 km/h.

What is the warmest month in Portsmouth?

The warmest month in Portsmouth is July (24.3 °C on average); the coldest is January (0.2 °C).

How much does it rain in Portsmouth?

Portsmouth receives on average 1,078 mm of precipitation per year, spread over about 131 rainy days.

Is it sunny in Portsmouth?

Portsmouth gets on average 8.7 hours of sunshine per day, roughly 3,175 hours per year over 1940-2025.

What is the biggest single-day snowfall in Portsmouth?

The heaviest 24-hour snowfall measured in Portsmouth between 1940 and 2025 was 4 February 1998, with 30.2 cm.

Are there tropical nights in Portsmouth?

Yes: Portsmouth has on average 42 tropical nights per year (temperature staying above 20 °C), over 1940-2025.

What was the most extreme apparent temperature in Portsmouth?

In Portsmouth, between 1940 and 2025, the highest apparent temperature reached 44.2 °C on 14 July 1954, and the lowest was -34.4 °C on 17 January 1977.

Compare Portsmouth with another city

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