Updated: 2026-08-14
A typical summer day in London brings a maximum of 21.9°C and a minimum of 13.2°C, with a daily mean of 17.6°C — measured across all June, July, and August days at St James's Park from 1912 through 2025. That is your baseline: warm enough for a short-sleeve morning, cool enough for a light jacket by midnight.
What a normal summer day feels like — not a heatwave, not a cold snap, just the long-term average. The warmest month in the seasonal cycle is July, with a mean maximum of 22.6°C, but August stays remarkably close at 22.3°C. June trails with 20.8°C, still comfortably above the 20°C mark.
The figures come from the official Met Office MIDAS weather station network, specifically the long-running London St James's Park site (station reference 00697). The series spans from 1912-01-01 to 2025-12-31, giving more than a century of daily observations. These are not model estimates or reanalysis products—they are the actual recorded temperatures from one of the UK's most central climate stations.
If you are planning a summer trip or an outdoor event in London, the numbers above are your practical guide. A typical July day warms up to 22.6°C, but the same day drops to an average minimum of 18.3°C overnight. That means mornings and evenings are noticeably cooler than the afternoon peak—a pattern that holds through all three summer months:
The table below breaks down the average maximum and average mean temperature for each calendar month across the full 1912-2025 period. July is the warmest month on average, August is a close second, and June is the entry point to the summer season.
| Month | Avg. max (°C) | Avg. mean (°C) |
|---|---|---|
| January | 7.7 | 5.2 |
| February | 8.2 | 5.5 |
| March | 10.9 | 7.5 |
| April | 13.9 | 10.0 |
| May | 17.7 | 13.4 |
| June | 20.8 | 16.3 |
| July | 22.6 | 18.3 |
| August | 22.3 | 18.0 |
| September | 19.7 | 15.7 |
| October | 15.5 | 12.1 |
| November | 10.9 | 8.1 |
| December | 8.6 | 6.1 |
Summer in London is not defined by extreme heat. The average maximum of 21.9°C sits well below the heatwave thresholds that make international headlines. Yet the daily mean of 17.6°C tells you that the season is genuinely mild, not just tolerable. Over the 114 years of records, the patterns have remained remarkably coherent: July's 22.6°C average maximum is the high point, and June's 20.8°C is the lowest of the three summer months.
For visitors, the practical takeaway is the spread between day and night. Even in August, the warmest month for minimums, the overnight average is 18.0°C—a full 4.3°C below the daytime peak. You will rarely need air conditioning, but you will need a layer for the evenings. That is the true signature of a London summer.
Looking at the seasonal cycle beyond summer, the coldest month is January with an average maximum of 7.7°C and a mean of 5.2°C. The sharpest jump comes between April and May, when the average maximum climbs from 13.9°C to 17.7°C. From May onwards, the city warms steadily into the summer peak, then cools gradually through autumn. The consistency of these numbers across a century of records makes them a reliable planning tool.
Whether you are scheduling a wedding, a festival, or simply packing for a holiday, the 21.9°C maximum and 13.2°C minimum give you the honest expectation. There will be warmer days and cooler days, but this is the climatological norm—the baseline against which every London summer is measured.
Source: Met Office MIDAS station at London St James's Park, 1912–2025. Official national climate data.
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© 2026 HistoClima · data: Met Office (OGL v3.0) · not affiliated with Met Office · citation permitted with source.