Autumn warmth peaks on Tuesday before Atlantic low brings gales to western Britain

Britain is set for a final surge of late-September warmth before a broad Atlantic depression sweeps in with wind, rain and localised gales, according to the BBC Weather Centre. A vast area of low pressure out in the Atlantic is expected to draw warm air northward on a strengthening southerly to south-easterly wind, but for many parts of the country the sunshine will come with a weather front not far behind it.

Lead Weather Presenter Helen Willetts, reporting from the BBC Weather Centre, said Tuesday is likely to be the warmest day of the week, with a swathe of England and Wales reaching between 20C and 26C. Scotland and Northern Ireland will be cooler but still mild, with temperatures in the high teens expected. After Tuesday, she said, values will generally retreat to something closer to the September average, ending what has been an unusually warm month for many areas.

The timing of the warm spell matters, because it arrives just after the autumn equinox. Longer nights now mean the sun can still feel strong while temperatures drop away sharply after dark, and Willetts noted that despite the warmth of recent afternoons, some cooler nights are expected under clear skies. Monday morning is expected to be notably chilly, with patches of fog likely to linger — a potential hazard for early commuters.

Once that early fog lifts, Monday should brighten considerably. High pressure is expected to allow sunny spells broken by only a few scattered showers. The exception is the south-east of England, where some welcome rain could fall through the afternoon and evening, though the forecast team stressed that is by no means guaranteed. Temperatures on Monday will range from the mid to high teens, with some southern areas reaching 20C.

The main event arrives on Tuesday afternoon. Rain is forecast to move into Northern Ireland during the afternoon and then track slowly eastwards through the evening and overnight. Willetts warned it could become persistent and occasionally heavy, accompanied by strong winds, with gales likely for exposed coasts and hills. Further east, drier and brighter conditions may hold on for longer before the rain finally arrives on Wednesday — and it may then linger into the night.

Wednesday itself brings a return to a more familiar British pattern. Behind the rain band, forecasters expect sunny spells and scattered showers, with the wind still blustery in the west. By Thursday, high pressure is expected to rebuild, allowing conditions to settle down considerably and turn calmer and drier. Then on Friday, the north-west becomes the focus for any showers — a pattern Willetts said is entirely typical for the season.

The wider context is a September that has split the country down the middle. Following the UK's hottest summer on record, September has been another notably warm month for many, but it has also exposed a stark contrast between the north-west and the south-east. Scotland and other western districts have repeatedly been hit by Atlantic weather systems carrying rain and wind, while much of central, southern and eastern England has stayed largely dry, with plenty of sunshine but correspondingly little rainfall.

Rainfall totals tell the story starkly. Some drought-affected parts of England have received very little, whereas parts of the north-west Scotland have been very wet. Kirkwall and Prestwick have already accumulated nearly one-and-a-half times their average September rainfall, and at Achnagart in the Highlands, rain has been recorded every single day for the past 27 days. By contrast, parts of Northern Ireland and Wales have picked up roughly their average totals, and north-east England has seen some of the lowest amounts so far.

That imbalance matters for the drought-affected regions, where forecasters say the incoming Atlantic weather is unlikely to deliver meaningful relief. Much of the UK is expected to see a spell of wetter and windier weather from the approaching depression, with the most unsettled conditions likely to affect Scotland, Northern Ireland and the western parts of England and Wales. However, many central, southern and eastern areas of England may see far less rain — meaning the dry spell, rather than ending, could persist through the week despite the change in pattern.

The contrast between very wet western Scotland and parched eastern England illustrates just how uneven the UK's rainfall can be over a single month, and why a wet Atlantic week does not automatically translate into drought relief. The BBC Weather Centre has previously reported research suggesting it could take at least seven months of relentless rain to end the drought affecting parts of England, a timescale far beyond the reach of a single frontal system.

Forecasters cautioned, as ever, that details may change. Anyone planning travel, outdoor work or travel exposed coastal routes — where gales are a possibility on Tuesday night — was advised to stay up to date with the short-term forecast for their area. Even so, the overall shape of the week is settled: a cold, foggy start, a warm and windy climax on Tuesday, a wet and blustery Wednesday, and a calmer, drier finish as high pressure returns by the end of the week.