Why UK weather turned unusually warm — and why rain is following

UK weather turned unusually warm on Tuesday 29 September as southerly winds drew warm air north ahead of an Atlantic low, while the same evolving system brought wind and rain. The Met Office’s Wednesday forecast points to showers and gradually easing winds, with temperatures still above average.

The striking figure is 28.1°C at Kew Gardens on Tuesday, reported by the Met Office. That was higher than the widely reported advance forecast of up to 27°C around London. The forecaster described the warmth as notable for late September, but not record-breaking.

Why is the UK so warm in late September?

The explanation starts with the direction of the wind. In her 28 September report, ITV weather presenter Lucy Verasamy explained that an Atlantic low moving north would establish southerly winds, carrying warmth from continental Europe through France into Britain.

“It will mean some of the heat will be drawn up through France and into the UK,” Verasamy wrote. Her explanation connected the warm spell to the approaching airflow, rather than suggesting Britain needed clear skies or settled weather to become unusually mild.

Cloud, rain and strong winds were actually limiting how warm that air mass could become, the Met Office said. Even with those limits, conditions across much of England and Wales were well above average. Warmth and unsettled weather were parts of the same weather pattern.

Was 27°C a forecast or a measured temperature?

The 27°C figure was a forecast for Tuesday around London, not a measured Wednesday temperature. The Met Office’s Monday outlook predicted 24–25°C in parts of southern Britain, with 26°C or perhaps 27°C possible around the capital as afternoon sunshine developed.

Sky’s advance coverage also reported the prospect of an unusually mild night. Met Office spokesman Stephen Dixon forecast minimum temperatures around 19°C in some places, saying this “could feel a touch uncomfortable for some, particularly as we're in late September.” That was an expectation, not confirmation of an overnight reading.

The subsequent Kew Gardens figure is a reported observation. In its dated Tuesday analysis, the Met Office said temperatures had reached 28.1°C there. Its description does not establish a late-September record, and a reading at Kew should not be treated as the temperature across the whole country.

When is the rain expected to clear?

The change comes with a cold front moving in from the west. Monday’s outlook placed its approach on Tuesday evening and overnight, bringing heavier rain and stronger winds. Tuesday’s analysis expected the front to weaken as it crossed eastwards on Wednesday, leaving eastern and southeastern England with less persistent rain than areas farther west.

The Met Office’s national forecast, updated at 03:00 UTC on Wednesday 30 September, expected heavy rain to clear eastwards by midday. Sunny spells and showers were forecast to follow, mainly in western areas, with some showers potentially bringing isolated hail and thunder. That timing is a forecast, not confirmation that rain cleared everywhere by midday.

Behind the front, the Met Office expected air originating in polar regions to arrive after a long journey over the Atlantic. Along that route it gathers moisture and becomes unstable, helping to produce showers. Wednesday’s forecast still kept temperatures above average, despite the change in air mass.

Winds were expected to ease gradually but stay gusty, especially in the west. For Wednesday night, the forecast kept scattered showers near western coasts, with generally dry conditions elsewhere. A cooler night was expected, particularly in eastern and southeastern areas, alongside isolated fog patches in sheltered places.

Will October start with drier weather?

For Thursday 1 October, the national forecast expected showers across parts of England and Wales to fade, leaving many places drier and brighter. Northern Ireland was forecast to become cloudier before rain arrived later, while northern and western areas remained windy.

The Friday-to-Sunday outlook retained a regional split: showers and wind at times in the north and west, with drier weather farther south. Temperatures were forecast to be near average in the north and above average in the south. It did not promise a uniformly dry UK weekend.

Saturday’s rain remained a particular uncertainty in the Met Office’s Tuesday analysis. Prolonged, sometimes heavy rain was a minority model outcome; many ensemble members instead indicated a shorter spell of showery rain followed by drier conditions. The wetter possibility could not be ruled out, but it had less support.