Portsmouth weather in May
In May, Portsmouth has daytime highs averaging 16 °C, nights around 9.0 °C, with 9.6 wet days, and a sea temperature of 11 °C. Figures are 1991–2020 climate normals.
- 15.9°C Average high
- 9.0°C Average low
- 9.6days Wet days
- 49mm Rainfall
- 11.4°C Sea temperature
- 16h Daylight
Daily temperatures through May
How May develops
Averages for the first, middle and last part of the month, from daily 1991–2020 normals. Chance of rain is the share of years in which that calendar day recorded more than 1 mm.
| Days | Avg high | Avg low | Chance of rain |
|---|---|---|---|
| 1–10 May | 14.8 °C | 7.7 °C | 29 % |
| 11–20 May | 15.6 °C | 8.8 °C | 33 % |
| 21–31 May | 17.1 °C | 10.3 °C | 32 % |
- Average highs rise from 14.8 °C early in May to 17.1 °C by the end of it.
What to expect
| Measure | Typical May | Share of the month |
|---|---|---|
| Days above 25 °C | 0 of 31 | 0 % |
| Days above 30 °C | 0 of 31 | 0 % |
| Days below 0 °C | 0 of 31 | 0 % |
| Days with more than 1 mm rain | 9.6 of 31 | 31 % |
Conditions in May
| Measure | Average |
|---|---|
| Mean temperature | 13 °C |
| Record high (1991–2020) | 25 °C |
| Record low (1991–2020) | 1.6 °C |
| Relative humidity | 76 % |
| Wind speed | 23 km/h |
| Cloud cover | 64 % |
May compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| 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 % |
See all twelve months for Portsmouth
- May is the 5th warmest month here.
- It is the 3rd driest month of the year.
- It ranks 6th for least cloud cover.
- Days last about 16 hours from sunrise to sunset.
- It rains on 9.6 of 31 days — 31 % of the month.
- Nights are about 6.9 °C cooler than the middle of the day.
- The hottest May day on record since 1991 reached 25 °C, 8.6 °C above the usual daytime high.
- Beach score: 18 / 100 — see how this is calculated.
QuestionsMay in Portsmouth, answered
How warm is Portsmouth in May?
Daily highs average 16 °C and nights fall to about 9.0 °C, a spread of 6.9 °C between afternoon and dawn. That makes May the 5th warmest month of the year here.
Does it rain much in Portsmouth in May?
May averages 49 mm of rain, spread over about 10 of the 31 days — 31 % of the month. Cloud cover averages 64 % of the sky.
Is the sea warm enough to swim in May?
The sea averages 11 °C off Portsmouth in May. Most people find water below 20 °C bracing and above 25 °C comfortable for a long swim; this figure is a monthly surface average, so a sheltered bay on a still afternoon can be warmer.
How long are the days in May?
Portsmouth averages 16 hours between sunrise and sunset in May. Day length is computed from latitude and date, so it is exact rather than modelled — but it says nothing about how much of that time is sunny.
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
Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: daylight hours, beach and comfort scores, monthly rankings, threshold day counts, chance of a wet day by date, ten-day averages within the month. 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.