Heavy rain on the M20 in Ashford, Kent. The Met Office is warning of flooding, road closures and power cutsGARETH FULLER/PA

Forecasters have warned of a “danger to life” from heavy downpours and the risk of severe flooding because a month’s worth of rain is predicted to fall over a few hours today.

The Met Office has upgraded its yellow rain warning to an amber weather warning, the second highest level, for London and most of the southeast of England. It says that flooding of homes and businesses, power cuts, train and bus delays and road closures are all likely.

“Fast flowing floodwater is possible, causing danger to life. After earlier rainfall some heavy, and perhaps thundery, showers are expected to develop over parts of southeast England. While many areas will miss the highest rainfall totals from these some places could see 50 to 60mm in…