Updated: 2026-08-12
If you are planning a trip to the UK capital and want the warmest, driest weather London can offer, the answer from the long-term climate record is clear: mid-summer, specifically the month of July, is your best bet. Based on the full Met Office historical series for St James's Park from 1912 to 2025, July holds the highest average temperature of any month, with a mean of 18.3°C and an average daily maximum of 22.6°C. For a city at this latitude, that is genuinely pleasant summer weather — warm enough for short sleeves in the park, yet rarely oppressive.
The runner-up is August, with an average temperature of 18.0°C and a mean maximum of 22.3°C. June is not far behind, averaging 16.3°C with daytime highs reaching 20.8°C. In short, the window from early June to late August offers London's most reliable warmth, with July delivering the peak of the summer season.
The warmest month in London's 113-year climate record is July, with an average temperature of 18.3°C
— that is the monthly mean across the entire period from 1912 through 2025, measured at St James's Park.
In practical terms, this means most July days in London sit comfortably in the low 20s, with the average daily maximum reaching 22.6°C. It is the month when outdoor terraces, riverside walks, and park picnics are most reliably pleasant.
The table below shows the complete monthly climatology for St James's Park, covering the full period from 1912 to 2025. Average temperatures, average daily maximum and minimum values, and mean precipitation are shown for each month. This is the definitive picture of what to expect on any given month if you are visiting London.
| Month | Mean Temp (°C) | Avg Daily Max (°C) | Avg Daily Min (°C) | Mean Precipitation (mm) |
|---|---|---|---|---|
| January | 5.2 | 7.7 | 2.8 | 1.8 |
| February | 5.5 | 8.2 | 2.8 | 1.3 |
| March | 7.5 | 10.9 | 4.1 | 1.5 |
| April | 10.0 | 13.9 | 6.0 | 1.6 |
| May | 13.4 | 17.7 | 9.1 | 1.5 |
| June | 16.3 | 20.8 | 11.9 | 1.7 |
| July | 18.3 | 22.6 | 14.0 | 1.6 |
| August | 18.0 | 22.3 | 13.8 | 1.9 |
| September | 15.7 | 19.7 | 11.7 | 1.8 |
| October | 12.1 | 15.5 | 8.8 | 1.8 |
| November | 8.1 | 10.9 | 5.3 | 1.9 |
| December | 6.1 | 8.6 | 3.6 | 1.9 |
Looking at the full seasonal cycle, London's climate is remarkably temperate. The coldest months, January and February, still average a mean temperature of 5.2°C and 5.5°C respectively, with daytime highs around 7.7°C and 8.2°C. This is not bitter cold; it is more a persistent damp chill, with frosts possible but rarely severe. The average minimum in both months is 2.8°C, so expect chilly mornings and evenings if you visit in the heart of winter.
Spring brings a steady climb: April averages 10.0°C and May 13.4°C, with May's average maximum reaching a comfortable 17.7°C. By late May, the city parks are in full bloom and outdoor dining becomes genuinely pleasant, though a light jacket is still wise for the evening.
Autumn, meanwhile, holds onto summer warmth for a surprisingly long time. September still averages 15.7°C with daytime highs hitting 19.7°C, often delivering "Indian summer" spells that rival June. October drops to 12.1°C on average, which is still mild enough for sightseeing, but November falls to 8.1°C as the city edges back toward winter.
One of the striking features of London's climate is how evenly precipitation is spread across the year. Unlike many European cities that have a clear wet season and dry summer, London's monthly mean precipitation ranges only from 1.3 to 1.9 mm across the entire calendar. Interestingly, February is the driest month with 1.3 mm, while August, November, and December share the top wet-month value at 1.9 mm each.
This means that, in terms of rain, no month is dramatically better or worse than any other. The practical takeaway for visitors is that you should pack a raincoat or umbrella regardless of when you come — but you should also know that a rainy day in July is just as likely as one in January, and that a dry spell can happen in any month. The difference between months is so small that temperature, rather than rain, should be your primary guide for choosing travel dates.
If you are considering a winter visit for Christmas markets or museum marathons, December offers a mean temperature of 6.1°C with average highs of 8.6°C — crisp but rarely freezing. The same is true of January and February, both with average minima of 2.8°C. Days are short, and the combination of cold air and urban heating gives London its characteristic damp winter feel. But for those who prefer fewer crowds and don't mind bundling up, the winter months are perfectly viable, with the added advantage of the lowest precipitation of the entire year in February (1.3 mm).
If your priority is the safest bet for warm, pleasant weather, July is the clear winner: the warmest average temperature at 18.3°C, the highest daily maxima at 22.6°C, and precipitation of just 1.6 mm, right in the middle of the range. August is statistically a near-twin, at 18.0°C and 22.3°C, with only marginally more rain (1.9 mm). The two months together form the core of London's summer — the best window for outdoor events, park concerts, river cruises, and open-air theatre.
June, while slightly cooler at 16.3°C on average, has the advantage of longer daylight hours and an average maximum of 20.8°C that is perfectly comfortable. For many visitors, the "shoulder" weeks of late May through mid-June or early September offer a sweet spot: nearly summer warmth without the peak-season crowds of July and August. September's 15.7°C average and 19.7°C average maximum make it an excellent choice for those who prefer a quieter city.
These figures come from the daily records of the St James's Park weather station in central London, one of the UK's longest-running urban observation sites. The station's archive includes daily temperature and precipitation measurements that begin on 1912-01-01 and extend through the most recent complete year, 2025-12-31. For each month, the daily values were aggregated to produce the long-term monthly mean — a total of 113 full calendar years of observations forming the basis of every number in the table above.
This is the same class of data used by climatologists to track long-term changes in the UK's capital, and it represents one of the longest continuous urban weather records in the country. That depth of history is what makes it possible to speak about London's weather not in terms of any single year — which can be anomalous — but in terms of what visitors should genuinely, statistically expect.
Source: Met Office, St James's Park station (London), period: 1912–2025
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© 2026 HistoClima · data: Met Office (OGL v3.0) · not affiliated with Met Office · citation permitted with source.