Portsmouth weather in July
In July, Portsmouth has daytime highs averaging 21 °C, nights around 14 °C, with 9.7 wet days, and a sea temperature of 16 °C. Figures are 1991–2020 climate normals.
- 20.7°C Average high
- 14.0°C Average low
- 9.7days Wet days
- 49mm Rainfall
- 16.4°C Sea temperature
- 16h Daylight
Daily temperatures through July
How July 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 July | 20.1 °C | 13.5 °C | 34 % |
| 11–20 July | 20.7 °C | 14.0 °C | 29 % |
| 21–31 July | 21.2 °C | 14.3 °C | 31 % |
- Average highs rise from 20.1 °C early in July to 21.2 °C by the end of it.
- Rain is most likely over days 1–10 of July (34 % of days) and least likely over days 11–20 (29 %).
What to expect
| Measure | Typical July | Share of the month |
|---|---|---|
| Days above 25 °C | 2.8 of 31 | 9 % |
| Days above 30 °C | 0.03 of 31 | 0 % |
| Days below 0 °C | 0 of 31 | 0 % |
| Days with more than 1 mm rain | 9.7 of 31 | 31 % |
Conditions in July
| Measure | Average |
|---|---|
| Mean temperature | 17 °C |
| Record high (1991–2020) | 30 °C |
| Record low (1991–2020) | 8.4 °C |
| Relative humidity | 75 % |
| Wind speed | 22 km/h |
| Cloud cover | 60 % |
July compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| 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 % |
See all twelve months for Portsmouth
- July is the warmest month in Portsmouth.
- It is the 5th driest month of the year.
- It ranks 1st for least cloud cover.
- Days last about 16 hours from sunrise to sunset.
- It rains on 9.7 of 31 days — 31 % of the month.
- Nights are about 6.8 °C cooler than the middle of the day.
- The hottest July day on record since 1991 reached 30 °C, 9.5 °C above the usual daytime high.
- Beach score: 43 / 100 — see how this is calculated.
QuestionsJuly in Portsmouth, answered
How warm is Portsmouth in July?
Daily highs average 21 °C and nights fall to about 14 °C, a spread of 6.8 °C between afternoon and dawn. That makes July the 1st warmest month of the year here.
Does it rain much in Portsmouth in July?
July averages 49 mm of rain, spread over about 10 of the 31 days — 31 % of the month. Cloud cover averages 60 % of the sky.
Is the sea warm enough to swim in July?
The sea averages 16 °C off Portsmouth in July. 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 July?
Portsmouth averages 16 hours between sunrise and sunset in July. 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.