Portsmouth, United Kingdom Climate & Monthly Averages
Portsmouth has an oceanic climate. July is the hottest month, averaging 70° by day; January is the coldest at 47°.
How weather changes through the year in Portsmouth
Weather in Portsmouth follows a oceanic pattern. The warmest and coolest months, July and January, average 70°F (21°C) and 47°F (8°C) by day; nights in those months run 58°F (15°C) and 38°F (3°C).
Portsmouth climate quick facts
- Hottest month: July - highs near 70°F (21°C)
- Coldest month: January - highs near 47°F (8°C)
- Decade extremes (2015-2024): 87°F (30°C) high · 24°F (-4°C) low
- Wettest month: October (14 rainy days) · Sunniest: June (12.1 h sun/day)
- Climate type: oceanic
- Annual swing: 12°C between the average warmest and coolest month · day to night: 6°C
- Snow: about 1 days a year
- Average humidity: 80%
Temperatures, rain and sunshine
January is the coolest month, with highs of 47°F (8°C) and lows near 38°F (3°C). July is the warm end of the year, averaging 70°F (21°C) by day and 58°F (15°C) overnight. Four of the twelve months pair mild highs with fewer than twelve wet days; the longest unbroken run is June through September.
Days and nights are about 6°C apart on average - narrower than all but 7% of the 3496 cities in our dataset. June is the brightest month at 12.1 hours of sun a day, against an annual average of 8.1 - duller than about 81% of the cities we track. The gridded 2015-2024 daily record for this location tops out at 87°F (30°C) and bottoms at 24°F (-4°C) - decade extremes, not all-time station records.
Where Portsmouth sits among other climates
- Portsmouth sits close to the middle of our dataset on most measures: 53°F (12°C) as an annual average, 33.4 inches (849 mm) of precipitation and 8.1 hours of sun a day.
These comparisons use the same ten-year window for every city in the dataset.
Monthly climate table
| Month | High | Low | Rain days | Precipitation | Sunshine | Daylight | Wet-day chance | Humidity |
|---|---|---|---|---|---|---|---|---|
| January | 47° | 38° | 13 | 3.1 in | 4.5 h/day | 8.4 h | 41% | 85% |
| February | 48° | 39° | 12 | 2.8 in | 5.3 h/day | 9.9 h | 43% | 83% |
| March | 51° | 41° | 13 | 2.8 in | 7.0 h/day | 11.7 h | 43% | 81% |
| April | 55° | 43° | 9 | 1.7 in | 10.1 h/day | 13.7 h | 30% | 76% |
| May | 61° | 49° | 11 | 2.2 in | 11.4 h/day | 15.5 h | 35% | 76% |
| June | 67° | 54° | 10 | 2.2 in | 12.1 h/day | 16.5 h | 35% | 76% |
| July | 70° | 58° | 11 | 2.3 in | 12.0 h/day | 16.1 h | 35% | 75% |
| August | 70° | 58° | 11 | 2.8 in | 10.5 h/day | 14.5 h | 36% | 78% |
| September | 66° | 55° | 11 | 2.8 in | 8.9 h/day | 12.5 h | 38% | 79% |
| October | 60° | 51° | 14 | 3.9 in | 6.6 h/day | 10.6 h | 44% | 82% |
| November | 53° | 45° | 13 | 3.4 in | 4.8 h/day | 8.8 h | 42% | 84% |
| December | 50° | 42° | 13 | 3.6 in | 3.7 h/day | 8.0 h | 42% | 86% |
Portsmouth month by month
Each card shows the average high and low. The bar places that month between Portsmouth's coldest night and warmest afternoon.
January
- Rain
- 13 days
- Sunshine
- 4.5 h
- Daylight
- 8.4 h
February
- Rain
- 12 days
- Sunshine
- 5.3 h
- Daylight
- 9.9 h
March
- Rain
- 13 days
- Sunshine
- 7.0 h
- Daylight
- 11.7 h
April
- Rain
- 9 days
- Sunshine
- 10.1 h
- Daylight
- 13.7 h
May
- Rain
- 11 days
- Sunshine
- 11.4 h
- Daylight
- 15.5 h
June
- Rain
- 10 days
- Sunshine
- 12.1 h
- Daylight
- 16.5 h
July
- Rain
- 11 days
- Sunshine
- 12.0 h
- Daylight
- 16.1 h
August
- Rain
- 11 days
- Sunshine
- 10.5 h
- Daylight
- 14.5 h
September
- Rain
- 11 days
- Sunshine
- 8.9 h
- Daylight
- 12.5 h
October
- Rain
- 14 days
- Sunshine
- 6.6 h
- Daylight
- 10.6 h
November
- Rain
- 13 days
- Sunshine
- 4.8 h
- Daylight
- 8.8 h
December
- Rain
- 13 days
- Sunshine
- 3.7 h
- Daylight
- 8.0 h
Looking for warmer alternatives? Browse warm places by month, or compare Portsmouth's coolest part of the year: January, February, December.
A season-by-season guide to Portsmouth
Spring (March through May)
Through spring, Portsmouth is mild: 56°F (13°C) by day, 44°F (7°C) after dark, and rain falls on around 33 of the 90 days.
Summer (June through August)
Summer brings comfortable warmth here - highs near 69°F (20°C), nights near 57°F (14°C), and rain falls on around 33 of the 90 days. Daylight is generous - around 11.5 hours of sun a day.
Fall (September through November)
Through fall, Portsmouth stays on the cool side of mild: 59°F (15°C) by day, 50°F (10°C) after dark, and rain falls on around 38 of the 90 days.
Winter (December through February)
Winter in Portsmouth stays firmly cold, with daytime highs averaging 48°F (9°C) and nights around 40°F (4°C); rain falls on around 38 of the 90 days.
Questions people ask about Portsmouth's climate
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The most useful weather window for Portsmouth
Best time to visit Portsmouth
May to September is the sweet spot for Portsmouth - warm days, manageable rainfall and plenty of daylight line up. Expect 67°F (19°C) in the afternoon and around 11 days of rain in a typical month of it. For the same question asked the other way round, see where else is warm in May.
What to pack
Pack for Portsmouth with a warm jacket and layers for the cooler season and proper waterproofs rather than an umbrella - wet days are the norm here. July nights average 58°F (15°C), so evenings rarely match the afternoons.
Portsmouth temperature extremes in the 2015–2024 dataset
Derived from ERA5 reanalysis data, 2015–2024. Official station records may differ. Need another precipitation unit? Use the rainfall converter.