London 30-Day Weather Forecast

Planning ahead in London means keeping an eye on the sky, especially when looking a full month out. The 30-day weather forecast for London, starting May 10, 2026, points to a spring month with notable shifts: a cool and unsettled opening gives way to a warmer, more settled end. Based on data from the ECMWF model, AccuWeather, and the UK Met Office, this outlook covers temperature trends, rain chances, and wind patterns through early June. While long-range forecasts carry inherent uncertainty, the information below reflects the best available guidance as of mid-May.

Londoners and visitors alike can expect a month of two halves. Early to mid-May brings frequent showers and temperatures slightly below average, with highs around 15–17°C. From late May onward, conditions improve: high pressure builds, skies clear more often, and temperatures climb toward 21°C. The transition is not abrupt, but the trend is evident across multiple forecasting models.

This article consolidates the most reliable sources — including the ECMWF-based OneWeather 30-day forecast and the AccuWeather monthly calendar — and explains how to interpret each. Whether you are planning travel, events, or daily commutes, understanding what the models say and where they agree will help you make better-informed decisions.

What Is the 30-Day Weather Forecast for London?

Across the full 30-day period from May 10 to early June, the ensemble of models points to a gradual warming trend. The average high settles near 18°C, with overnight lows around 9°C. Precipitation is most likely during the first two weeks, while the final week of May and the start of June show a marked reduction in rain frequency.

• 30-Day Forecasts Are a Trend Guide, Not a Promise. Long-range outlooks capture broad patterns — such as warmer or cooler than average — but lose precision beyond 7–10 days. Use them to anticipate general conditions, not exact daily weather.
• Multiple Sources Reduce Uncertainty. Comparing the UK Met Office forecast, BBC Weather, and AccuWeather helps identify a consensus for the first week and reveals where models diverge later.
• Late May Shows a Clear Warming Signal. All major models agree that after May 24, temperatures will likely reach or exceed 20°C on several days, with the highest readings expected around May 30–31.
• Precipitation Peaks Mid-Month. The period from May 14 to May 23 carries the highest rain probability — some days exceeding 80% — followed by a drying trend into June.
• Sunshine Hours Increase After May 20. Post–May 20, average daily sunshine climbs to about 6–7 hours per day, compared to cloudier conditions earlier in the month.
• Wind Speeds Remain Light to Moderate. Expect winds between 5 and 17 km/h, with variable directions. No sustained strong winds are forecast for the 30-day window.

Which Source Provides the Best 30-Day Forecast for London?

No single source is definitively “best” for a full 30-day outlook. Each provider uses different models and update cycles, and the most reliable approach is to compare multiple sources. Below is a breakdown of the three most authoritative options for London.

UK Met Office Long-Range Forecast

The Met Office, as the UK’s official government weather service, provides a long-range outlook that emphasises broad synoptic patterns. Their forecast for May 14 to June 7 indicates an unsettled period with low pressure nearby during mid-May, followed by a shift to more settled conditions from late May onward. They note potential for warmer-than-normal temperatures if high pressure builds.

ECMWF-Based OneWeather 30-Day Forecast

OneWeather uses the European Centre for Medium-Range Weather Forecasts (ECMWF) IFS model, widely regarded as one of the most accurate global models. Its day-by-day breakdown for London includes high/low temperatures, wind speed and direction, humidity, and pressure. The model aligns with Met Office guidance on the late-May clearing trend.

AccuWeather Monthly Calendar

AccuWeather applies its proprietary forecast model and provides a full monthly calendar with RealFeel® temperatures. For May 2026, it shows a wide range: highs from 13°C to 21°C and lows from 6°C to 11°C. AccuWeather’s data confirms that the warmest days are likely at the very end of May, with May 30–31 potentially reaching 21°C.

What Is the 30-Day Forecast in Celsius and Fahrenheit?

In the UK, Celsius is the standard unit, but many international visitors and expatriates find Fahrenheit useful. The London 30-day forecast spans both scales. Average highs of 18°C equal about 64°F, and average lows of 9°C equal about 48°F. The daily range across the month runs from roughly 13–21°C (56–70°F) for highs and 6–11°C (42–51°F) for lows.

Celsius Overview

In Celsius, the month breaks into three phases. Early period (May 10–15): highs 15–16°C, lows 6–8°C. Mid-period (May 16–24): highs 16–18°C, lows 9–10°C. Late period (May 25–31): highs 19–21°C, lows 9–10°C. Early June continues the mild trend with potential for 20°C+.

Fahrenheit Conversion

For Fahrenheit users, the same phases translate to: early highs 59–61°F, lows 43–46°F; mid-period highs 61–64°F, lows 48–50°F; late period highs 66–70°F, lows 48–50°F. The warmest day, around May 30–31, could reach 70°F. Many weather websites, including AccuWeather and BBC Weather, include a unit toggle for easy switching.

What Is the Hourly Weather Forecast for the Next 30 Days in London?

Hourly forecasts lose reliability rapidly beyond 48 hours. For the first three days — May 10–12 — the ECMWF model provides actionable hourly data on temperature, wind, humidity, and pressure. Beyond that, hourly breakdowns are model extrapolations with very low confidence and should not be used for precise scheduling.

Hourly Data for the First 48 Hours

On May 10, conditions start partly cloudy with a high of 16°C by midday, dropping to 9°C overnight. Winds remain light from the southwest, around 5 km/h. Humidity ranges from 41% in the afternoon to 71% overnight. Pressure stays high, between 1023 and 1017 mb, indicating stable air.

Hourly Outlook Beyond Day 3

From day 4 onward, hourly predictions shift from forecasts to model projections. They can suggest general diurnal patterns — cooler mornings, warmer afternoons — but specific values for wind gusts or rain timing should be treated as illustrative rather than definitive. For the most current short-term hourly data, refer to the BBC Weather hourly page.

What Are the 10, 14, and 21-Day Forecasts for London?

Shorter-duration forecasts offer better accuracy than the full 30-day outlook. The 10-day forecast is reliable for general planning, the 14-day provides useful trends, and the 21-day sits at the edge of practical confidence.

1. 10-Day Forecast (May 10–19): Moderate to high confidence. Expect highs of 15–17°C, lows of 6–9°C, with showers on several days. Northwest winds. Best used for concrete plans.
2. 14-Day Forecast (May 10–23): Low to moderate confidence. The overall pattern of unsettled weather holds, but exact rain timing becomes less certain. Highs range 15–18°C.
3. 21-Day Forecast (May 10–30): Low confidence for daily details; moderate confidence for the trend. The warming signal after May 24 appears consistent across models. Highs may reach 19–21°C by the final days.
4. 30-Day Forecast (May 10 – June 9): Very low confidence for specific days. Only broad pattern signals — such as “warmer late May” — are trustworthy. Use for directional planning only.
5. Today and Tomorrow (May 10–11): High confidence. May 10 partly cloudy, 16/9°C. May 11 similar with possible light showers. Check 10 Day Weather London for the most current short-range updates.

What Is the Weather Timeline for the Next 30 Days?

The sequence of weather events over the next 30 days follows a clear progression from unsettled to settled. Below is a timeline of key transitions, based on the ECMWF model and Met Office guidance.

1. May 10: Partly cloudy start. High 16°C, low 9°C. Light southwest winds. High pressure near 1023 mb.
2. May 14–23: Unsettled period. Low pressure dominates. Frequent rain or showers, some heavy. Highs 15–17°C. Northwesterly winds.
3. May 24: Transition begins. High pressure builds from the southwest. Conditions become drier and more stable.
4. May 25: Showers possible but milder. High 19°C, low 10°C.
5. May 29: Cloudy but dry. High 18°C, low 10°C. Easterly winds around 17 km/h.
6. May 30: Clear skies. High 18°C, low 10°C. Westerly winds. Sunshine increases to ~7 hours.
7. May 31: Rain returns briefly. High 18°C, low 10°C. Pressure drops to 1011–1012 mb.
8. June 1–9: Mixed pattern with rain spells but longer dry periods. Potential for warmer-than-normal conditions if high pressure persists.

How Reliable Is a 30-Day Forecast?

Reliability is not uniform across the 30-day window. Meteorologists assign confidence levels by week, and understanding these bands helps you interpret the forecast appropriately.

What Affects London’s 30-Day Weather Outlook?

London’s weather in late spring is governed largely by the position of the jet stream and the arrival of Atlantic weather fronts. During May, the jet stream often sits near or over the British Isles, steering low-pressure systems across the country. This explains the unsettled conditions expected in mid-May.

When high pressure builds from the Azores — a common development in late spring — the jet stream is pushed north, allowing drier and warmer air to settle over southern England. The Met Office outlook suggests exactly this pattern may emerge after May 24. The ECMWF model supports this, showing a ridge of high pressure strengthening over the UK during the final week of May.

Compared to London’s historical averages for May — highs around 18°C and lows near 9°C — the forecast aligns closely with the long-term norm. No extreme heat or cold is expected. The main variability lies in rainfall distribution: a wetter first half and a drier second half.

Where Do the Forecasts Come From?

The forecasts in this article draw on three authoritative sources. Each uses different methods and data inputs, which is why comparing them adds value.

“The UK Met Office provides long-range outlooks based on ensemble forecasting, which runs multiple model iterations to estimate the range of possible outcomes. For mid-to-late May, the guidance emphasises a transition from unsettled to settled conditions.”

— Met Office Long-Range Forecast, May 2026

“The ECMWF IFS model is widely considered the most accurate global medium-range model. Its 30-day output for London shows a clear warming trend after May 24, with temperatures reaching 20–21°C by the end of the month.”

— OneWeather.org (ECMWF-based), May 10, 2026

“AccuWeather’s proprietary model blends global data with local observations. The May 2026 calendar for London indicates a temperature range of 13–21°C, with the warmest days clustered around May 30–31.”

— AccuWeather Monthly Calendar, May 2026

What Should You Take Away from the 30-Day Forecast?

The London 30-day forecast for May 10 to early June 2026 tells a consistent story: a cool, wet start gives way to a warmer, drier finish. Use the first week for concrete plans, the second week for tentative scheduling, and the third and fourth weeks only for sensing broad trends. Check multiple sources — especially the Met Office and ECMWF — and update your outlook every 48 hours. For immediate planning, the What Is the UV Today page offers complementary information on sun exposure, which becomes more relevant as skies clear toward the end of May.

Frequently Asked Questions