Thunderstorms are set to deluge parts of London on Sunday night, according to the Met Office.
Yellow weather warnings have been issued for areas including London and the south-east, south-west England and parts of Wales.
Forecasters said the heavy thunder could result in sudden flooding, lightning strikes and possible “localised disruption”.
Road closures, power cuts and damage to trees and buildings are possible.
The Met Office warns: “A band of heavy showers and thunderstorms will move quickly eastwards today, giving a period of intense rain and perhaps 15-20mm of rain in a few places in an hour or less.
“These may be accompanied by lightning, hail and strong winds, with a low risk that some places could see gusts of 50mph.”
Warnings for wind and snow are also in place for northern Scotland on Tuesday and Wednesday.
Showers and strong winds may cause difficult driving conditions on higher routes. Bus, ferry and train services could be affected, with trips taking longer than usual or cancelled.
The Met Office warnings adds: “Frequent snow showers and gusts to severe gale force are expected on Tuesday, leading to travel disruption, particularly for higher routes.”