An amber weather warning has been issued by the Met Office as parts of England and Wales are braced for heavy rain.
The warning for rain is in place until 21:00 BST across parts of central England, while yellow rain warnings are in place more widely across much of the rest of England and large parts of Wales.
Affected areas could experience flooding as more than a month’s worth of rain is expected to fall on Monday, the Met Office says.
Rain warnings were in place over the weekend as summer officially drew to a close following the autumn equinox on Sunday afternoon.
Overnight, London and the Home Counties were worst affected by the conditions.
About a month’s worth of rain fell on parts of the Chilterns in four hours – most of it in just two hours.
In south east England, a night of heavy rain forced the closure of an M25 slip road and led to delays on train services.
While there is a risk of some passing torrential downpours in most areas in England and south-east Wales on Monday, parts of central and southern England will be the focus for more persistent heavy rain.
The area covered by the amber warning stretches from Herefordshire and Gloucestershire up towards East Anglia and the Humber, encompassing Birmingham, Nottingham and Sheffield.
Between 100 and 120mm of rain could fall on the worst affected areas on Monday, with further flooding and disruption likely.
Some areas will stay dry.
Looking ahead, another longer spell of rain will cross England and Wales during the day on Wednesday, but as that clears chillier air from the Arctic will move south across most of the UK for the end of the week.
Daytime temperatures on Friday will peak at just 8 to 13C.
