More than a month’s rain could fall in less than 24 hours in southern parts of the UK by the end of Sunday, and a Met Office warning is in place for severe thunderstorms that could cause life-threatening floods. Travel has already been disrupted by the downpours, which caused Exeter airport to cancel its remaining flights on Sunday, and 12cm (4.7 inches) of rain could fall in Taunton and Bridgwater in Somerset, according to the Met Office, which is more than the average rainfall for the whole of September. Videos posted on social media showed the main terminal at the airport flooded. An amber weather warning for thunderstorms and heavy persistent rain, with possible flooding across parts of Devon and Somerset, was put in place on Sunday, while a yellow warning for thunderstorms is in place across the rest of the south-west of England and south Wales. Yellow warnings for thunderstorms issued for London, the south-east and east of England and the East Midlands are expected to last until 6am on Monday. The Met Office said there was a small chance of thunderstorms becoming severe in the south-east of England, with large hailstones, frequent lightning, gusty winds and torrential rain producing 30 to 40 mm in an hour from late afternoon through Sunday night. Homes and businesses could also be in danger of flooding in torrential downpours, the Met Office said, with up to 70mm possible in some spots. A number of businesses have reportedly already flooded, and Avon and Somerset police have advised against non-essential travel with many roads closed. In Somerset and Devon, an additional 25mm to 50mm of rain is expected to fall in the affected area on top of the 30mm to 60mm that has already fallen in the past 12 hours as the thunderstorms move gradually towards the north-east across parts of south-west England. This will mean more than 100mm of rain may have fallen by the end of Sunday in an area where the September average is 92.45mm. Other parts of the UK could receive at least half a month’s rainfall in less than 24 hours. In areas with an amber warning, damage to homes and businesses is likely and could happen quickly, with fast-flowing or deep floodwaters posing a danger to life, the Met said. Spray and flooding is likely to lead to road closures and difficult driving conditions, and there is a chance of transport delays and power cuts. In areas with a yellow warning, there is a “small chance” conditions could pose a danger to life. Flooding to homes and businesses, power cuts, a loss of other services to homes and travel disruption are all also possible but less likely. Met Office meteorologist Jonathan Vautrey said it was worth checking the forecast before leaving home to know where the most severe thunderstorms were. “It is worth checking those things immediately before you head out on your journey so that you are aware where the most severe thunderstorms are possible. “Make sure you are taking care as the weather could change at very short lead times and just be prepared for those gusty winds and potentially large hailstorms,” he said. Conditions are expected to remain “blustery at times” early next week but are likely to be fresher. More thunderstorms are possible as the remnants of Hurricane Lee, which hit New England in the US and eastern Canada, is forecast to move across the UK between Tuesday and Thursday.