London weather: yellow storm warning as rain sweeps city
London weather is under a Met Office yellow thunderstorm warning as rain sweeps the capital, with intense downpours of up to 50mm possible in a few hours and a risk of flash flooding. Mayor Sadiq Khan urged Londoners to prepare, while showers overnight already brought about 8mm in places.
Key Takeaways
- A Met Office yellow thunderstorm warning covers London from 3am to 10pm on Wednesday.
- Forecasters warn 20–30mm could fall in under an hour, with 40–50mm possible in two to three hours.
- Overnight rain brought about 8mm in some spots, though thunderstorms had not yet materialised.
- Further wet spells are expected into the August bank holiday weekend, with forecasts still split on thunder.
- Hard, drought-baked ground raises the chance of surface water flooding.
According to the London Evening Standard, the yellow alert stretches across much of England, including London and the South East, the Midlands, East Anglia, and parts of the North West, South West, and eastern Wales.
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Why does the thunderstorm warning matter for Londoners?
The Met Office said Wednesday afternoon showers and thunderstorms “may be intense.” That intensity matters because dry, hard ground after a sustained hot summer can send water rushing over surfaces rather than soaking in.
On Tuesday afternoon, Mayor Sadiq Khan put the city on alert for flash floods. He warned that intense downpours could deliver up to 50mm in just a few hours—almost August’s average rainfall—and said from 3am London was at risk of severe flash floods.
Yellow alerts signal a small chance that homes and businesses could flood. The Met Office also flagged possible train and bus delays or cancellations, spray and difficult driving, some road closures, and a slight chance of power cuts where flooding or lightning strikes occur.
The rain arrives after London was declared under drought, with a hosepipe ban in force and parks left brown and dried out. Many residents will welcome the moisture even as flood risks rise.
Will London weather stay unsettled over the bank holiday?
The Standard reported Wednesday’s rain sits ahead of about five days of expected wet weather in the capital. Time Out’s bank holiday outlook, drawing on Met Office and BBC guidance, points to further disruption around Carnival weekend.
Friday 28 August is expected to be mostly rainy, with a chance of thunder and lightning from about 6pm to 8pm and highs near 22C. Saturday may see rain from midday and, on the BBC’s view, thunderstorms between 7pm and 8pm, again around 22C.
Sunday looks less wet, with only a chance of light drizzle and temperatures near 23C. Monday is tipped for sunny intervals, a moderate breeze, and about 22C.
My London noted an important split: the BBC sees a considerable chance of thunder on Friday and Saturday, while the Met Office foresaw Friday rain, a drier Saturday, and no thunder on either day. Short-range forecasts can shift, so checking updates remains wise.
Could Notting Hill Carnival be a washout?
Time Out reports that Notting Hill Carnival typically goes ahead rain or shine. Organisers and crowds are used to drizzle; an umbrella or waterproof jacket is the practical fix rather than a cancellation fear.
All Points East may feel the weather more. Friday’s worst rain should ease before Tyler, the Creator’s set, though light rain could linger into the evening. Saturday’s headliner slot carries a thunderstorm risk on the BBC forecast. Sunday’s lineup, including Twenty One Pilots, looks likelier to stay mostly dry.
Stargazers also have Friday’s partial lunar eclipse on the calendar. Royal Museums Greenwich said roughly 93 percent of the Moon would be covered at peak—impressive for UK viewers—if storm clouds do not block the view.