Weather in United Kingdom in August

August climate overview

Daytime highs across United Kingdom in August run from 19.0°C (Cornwall) to 21.4°C (London). Even in London only 12% of days reach 25°C. Nights average 13.8°C; the coldest 10% of nights in Cornwall fall to 12°C or below.

Rainfall in August

Expect around 12 rainy days (1 mm or more) in August, with London the driest (10 days) and Cornwall the wettest (13 days). The wettest August at London between 1991 and 2020 was 2010 with 117 mm; the driest was 1995 with 1 mm.

Sea temperature

The sea averages 16.6°C around United Kingdom in August. That is cold for swimming without a wetsuit.

Sunshine and daylight

Around 4.8 hours of sunshine a day on average, out of 14.4 hours of daylight (sunshine estimated from cloud cover).

August against the rest of the year in United Kingdom

August is the 2nd warmest month of the twelve in United Kingdom. It is 0.2°C cooler than July and 2.1°C cooler in September. The hottest month here is July (20°C) and the coolest January (8°C).

Which part of United Kingdom in August?

• Most sunshine: London, 5.1 h a day.
• Driest: London, about 10 rainy days.
• Warmest sea: Cornwall, 17°C.
• Hottest: London, 21°C by day.
• Coolest (better for walking and cities): Cornwall, 19°C.

What to pack for United Kingdom in August

Based on the averages: light layers - warm in the sun, cooler in the shade; a light jumper for evenings (14°C at night); a rain jacket - roughly 12 wet days.

Similar weather elsewhere in August

Within 1.5°C of United Kingdom's August daytime average: Amsterdam (21°C, sea 20°C). See the full ranking for August.

London for warmer days and less rain

Choose London over Cornwall if warmth and fewer rainy days matter most. London averages 21°C by day, which is comfortable for spending time outside without planning your whole day around the heat. Days above 25°C account for 12% of August days, so hotter weather is possible, but it should not be the basis of your packing. Bring light clothes alongside a layer for evenings, when the average falls to 14°C. With 10 rainy days, London is not a reliably dry option either. Keep outdoor plans flexible and carry a waterproof rather than assuming that a warm morning means a dry afternoon.

Cornwall for mild coastal weather, not warm-water swimming

Cornwall is the cooler choice, with daytime temperatures averaging 19°C and nights averaging 14°C. That makes it a reasonable fit for travellers who enjoy being outside in mild conditions and do not need strong heat to make a holiday feel worthwhile. Pack layers for time by the coast and something warmer for evenings. Rain is a bigger consideration here than in London: 13 rainy days make weather-dependent plans less dependable. Leave room to rearrange outdoor time rather than filling every day with activities that need dry weather. The sea averages 17°C, so treat swimming as a cool-water activity, not a promise of comfortable, lingering dips.