Portsmouth climate

Name: Portsmouth
Address: GB

Portsmouth is warmest in July, with average highs of 21 °C, and coldest in February, when nights average 3.3 °C. November is the wettest month (81 mm) and March the driest (47 mm). Figures are 1991–2020 climate normals.

Across a full year Portsmouth averages 714 mm of rain, 6 days above 25 °C and 17 days below freezing.

United Kingdom · population 208,100 · 1991–2020 normals

Temperature below 0 °C to above 30 °C Rain band height is that month’s share of the wettest month

Warmest month July 21 °C
Coldest month February 3.3 °C
Driest month March 47 mm
Wettest month November 81 mm
Least cloud July 60 % cloud
Hottest on record August 31 °C
Coldest on record February -7.4 °C
Warmest sea August 18 °C

What to expectPortsmouth through the year

Portsmouth has a clear annual cycle: average daily highs run from 8.1 °C in February to 21 °C in July, a swing of 12 °C in mean temperature across the year.

Counted across a normal year, 6 days a year reach 25 °C, 0 of them reach 30 °C, 17 nights drop below freezing. The warmest reading in the 1991–2020 record is 31 °C, in August.

Rain is spread fairly evenly through the year, from 47 mm in March to 81 mm in November. There is no dry season to aim for.

The sea off Portsmouth is warmest in August at 18 °C and coldest in March at 7.9 °C. Sea temperature lags the air by a month or two, which is why late summer swims warmer than early summer at the same air temperature.

Month by month

Month	Avg high	Rainfall	Cloud
January	8.0 °C	69 mm	72 %
February	8.1 °C	54 mm	69 %
March	10.3 °C	47 mm	68 %
April	12.8 °C	49 mm	61 %
May	15.9 °C	49 mm	64 %
June	18.6 °C	47 mm	64 %
July	20.7 °C	49 mm	60 %
August	20.6 °C	59 mm	62 %
September	18.3 °C	54 mm	62 %
October	14.7 °C	78 mm	67 %
November	11.0 °C	81 mm	70 %
December	8.5 °C	77 mm	71 %

Temperature month by month

Month	Avg high	Avg low	Mean	Record high	Record low	Days above 25 °C	Days below 0 °C
January	8.0 °C	3.6 °C	5.9 °C	14.0 °C	-6.1 °C	0	5
February	8.1 °C	3.3 °C	5.8 °C	14.5 °C	-7.4 °C	0	5
March	10.3 °C	4.4 °C	7.3 °C	18.0 °C	-4.2 °C	0	2
April	12.8 °C	6.0 °C	9.5 °C	22.7 °C	-1.5 °C	0	0
May	15.9 °C	9.0 °C	12.6 °C	24.5 °C	1.6 °C	0	0
June	18.6 °C	11.8 °C	15.4 °C	27.7 °C	4.7 °C	1	0
July	20.7 °C	14.0 °C	17.5 °C	30.2 °C	8.4 °C	3	0
August	20.6 °C	14.1 °C	17.4 °C	30.5 °C	8.4 °C	2	0
September	18.3 °C	12.2 °C	15.3 °C	26.5 °C	6.2 °C	0	0
October	14.7 °C	9.7 °C	12.3 °C	23.6 °C	-0.4 °C	0	0
November	11.0 °C	6.5 °C	8.8 °C	17.2 °C	-2.7 °C	0	1
December	8.5 °C	4.3 °C	6.4 °C	14.6 °C	-5.4 °C	0	4

Rain, sun and wind month by month

Month	Rainfall	Wet days	Daylight	Cloud cover	Humidity	Wind	Sea temp
January	69 mm	12	8.5 h/day	72 %	85 %	30 km/h	8.9 °C
February	54 mm	10	10 h/day	69 %	83 %	28 km/h	8.0 °C
March	47 mm	10	12 h/day	68 %	80 %	26 km/h	7.9 °C
April	49 mm	10	14 h/day	61 %	77 %	24 km/h	9.2 °C
May	49 mm	10	16 h/day	64 %	76 %	23 km/h	11.4 °C
June	47 mm	10	16 h/day	64 %	76 %	23 km/h	14.1 °C
July	49 mm	10	16 h/day	60 %	75 %	22 km/h	16.4 °C
August	59 mm	10	15 h/day	62 %	77 %	22 km/h	17.8 °C
September	54 mm	9	13 h/day	62 %	78 %	23 km/h	17.4 °C
October	78 mm	12	11 h/day	67 %	81 %	26 km/h	15.6 °C
November	81 mm	12	9.0 h/day	70 %	85 %	27 km/h	13.1 °C
December	77 mm	12	8.0 h/day	71 %	86 %	29 km/h	10.6 °C

How Portsmouth compares

The same four figures for nearby destinations, so the numbers above have something to be read against. Summer high is the warmest month's average high; winter low is the coldest month's average low.

Destination	Summer high	Winter low	Rain per year	Days above 25 °C
Portsmouth	21 °C	3.3 °C	714 mm	6
Southampton · United Kingdom	21 °C	3.0 °C	738 mm	6
Bournemouth · United Kingdom	20 °C	4.0 °C	749 mm	4
Brighton · United Kingdom	20 °C	3.4 °C	726 mm	2
Reading · United Kingdom	21 °C	2.1 °C	666 mm	10

Planning a trip? See the best time to visit Portsmouth.

QuestionsCommon questions about Portsmouth’s climate

When is the best time to visit Portsmouth?

That depends on what you want, so the honest answer is a comparison rather than a single month. June, July, August sit closest to 20 °C on average, July is the warmest month and March the driest. The month-by-month table above has the full picture.

How hot does Portsmouth get?

In July, the warmest month, daily highs average 21 °C. About 0 days a year pass 30 °C. The highest value in the 1991–2020 record is 31 °C.

How cold does it get in winter?

Nights average 3.3 °C in February, the coldest month. A normal year has 17 nights below freezing.

Which month is wettest in Portsmouth?

November, averaging 81 mm over 12 days with rain. The driest month is March with 47 mm. The year as a whole averages 714 mm.

Are these figures a forecast?

No. They are 1991–2020 climate normals: the average of thirty years, which describes what a month is usually like in Portsmouth rather than what any particular week will bring. Individual years can differ substantially from the normal.

Data sources and method

ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
Open-Meteo — Open-Meteo.com. CC BY 4.0
NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
GeoNames — GeoNames.org. CC BY 4.0

Normal period: 1991–2020
Dataset version: era5-1991-2020-scores1.1
Last processed: 1 August 2026

Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: monthly rankings, daylight hours, beach and comfort scores. Full formulas are on the methodology page.

Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.