Parts of Britain are set to experience unseasonably warm weather this afternoon, with temperatures reaching 27C before a powerful “weather bomb” arrives tomorrow.
Southern and eastern England are enjoying a late spell of summer-like warmth, almost a month after the season ended. Temperatures are expected to climb as much as 7C above the average for late September.
The warmth will continue overnight, with some areas facing the possibility of a “tropical night” — a term used when temperatures remain at or above 20C. Such conditions are highly unusual this late in September.
London is among the places where a tropical night could occur. Overnight temperatures there are typically between 7C and 11C at this time of year, making the expected warmth particularly striking.
However, conditions will become increasingly unsettled overnight as a weather front moves gradually from west to east. The system is expected to bring up to 1.5in (40mm) of rain and wind gusts reaching 50mph tomorrow.
Meteorologists are monitoring a deep area of low pressure over the Atlantic Ocean that is undergoing explosive cyclogenesis, a process commonly referred to as a “weather bomb”.
A weather bomb is officially defined as a low-pressure system whose central atmospheric pressure drops by at least 24 millibars within 24 hours.
Forecasters expect the system in the north-east Atlantic to deepen from 987mb to 955mb in a single day. That 32mb fall comfortably exceeds the threshold for a weather bomb.
The South began the morning under widespread cloud, although sunshine is expected to break through during the afternoon. In the North, a clear start will give way to increasingly cloudy skies.
Met Office chief forecaster Matthew Lehnert said: “A deep area of low pressure far into the Atlantic is the primary driver behind the UK’s weather over the next few days.
“Its first influence will help draw warmer air across much of the country on Tuesday, with temperatures likely to peak at 27C — notably high for this time of year.
“A warm night will follow across southern and eastern areas, with minimum temperatures of 19C in some locations.”
By this evening, western parts will become increasingly wet and windy as the weather front advances from west to east. Its passage will continue through the end of the day and into tomorrow.
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Met Office deputy chief forecaster Steven Keates said: “As this weather front moves slowly from west to east late on Tuesday and into Wednesday, many areas will receive around 10mm of rain. More than 40mm could fall in isolated spots on south-facing hills in the west.
“The unsettled conditions will also bring strong, gusty winds, with speeds above 50mph possible, particularly along exposed north-western coasts. Large waves could affect some western coastal areas as they coincide with high spring tides.”
Further rain and heavy showers are expected across many parts of the UK on Thursday and Friday, although some areas should see brighter, drier intervals.
High pressure is then forecast to build across much of the UK this weekend, reducing the likelihood of rain. Any lingering light showers are expected to remain largely confined to the far north-west.
Mr Keates added: “There is a good degree of confidence that high pressure will become more influential over the weekend, bringing plenty of dry and fine weather to many areas.
“Temperatures will generally be close to average for the time of year, and the area of high pressure is likely to remain in place at least into the start of next week.”
There had been speculation that the Met Office might name the first storm of autumn this week, but that now appears unlikely.
The first named storm of the 2026/27 season will be Storm Austen, in the partnership between the Met Office, Ireland’s Met Éireann and the Dutch service KNMI.
Met Éireann selected the name in honour of Austen Nagle, the Irish Meteorological Service’s first director; and for the fifth storm of the season, the weather service celebrated Evelyn Murphy, RTÉ’s first woman weather presenter.
In Ireland today, Met Éireann issued a series of yellow wind and rain warnings – but is also not expected to name the system as a storm, given there are no orange warnings in place.
It comes as much of England remains in drought after a very dry spring and summer that brought successive heatwaves, putting huge pressure on water supplies.
While the last month has finally brought some meaningful rain to parched areas, hosepipe bans remain in place with no prospect of being lifted soon.
Supercharged El Nino conditions in the Pacific – which affect weather across the world – are set to put the UK at greater risk of a wet and stormy autumn overall.
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