UK Braces for 25C Snap of Late-September Warmth Before Windswept Change

A burst of unseasonably warm weather is set to sweep across parts of the UK on Tuesday, with forecasters predicting temperatures could climb as high as 25C in the south-east of England.

The warmth will be carried northwards on a strong southerly airflow, drawing hot air up from France and Spain where temperatures have been widely exceeding 30C in recent days. That southerly wind will act as a conveyor belt, transporting some of that continental heat towards British shores.

While the highest readings will be concentrated in south-east England, where the mid-20s Celsius are expected, temperatures will broadly reach into the 20s across England. Elsewhere in the UK, the mercury will still climb into the high teens, making for a notably mild day for the time of year.

According to forecasters, these values will sit around 3 to 6 degrees above the seasonal average. Across England in late September, typical maximum temperatures hover between 16 and 19C, so Tuesday's warmth represents a significant departure from what would normally be expected as autumn takes hold.

The day will not be uniformly bright, however. Tuesday morning is likely to bring a good deal of cloud along with a few scattered showers. As the day progresses, sunny spells will develop across England and Wales, allowing the warmth to build and giving many areas a pleasant autumnal afternoon.

Wales, Northern Ireland and Scotland will also experience above-average temperatures, with maximums on Tuesday expected to range between 17 and 22C. But after a sunny start in these regions, cloud cover will increase as the day wears on, tempering the brightness somewhat.

The southerly winds themselves will strengthen as Tuesday unfolds. Gusts of up to 50mph are anticipated in Northern Ireland and western Scotland, linked to a large and deep area of low pressure that is moving north through the eastern Atlantic towards Iceland.

That contrast between the calm, warm conditions further south and the blustery, cloudier weather in the north-west illustrates how a single weather system can produce markedly different experiences across the country. While south-east England basks, parts of Scotland and Northern Ireland will feel the effects of the approaching Atlantic low.

What makes this spell particularly noteworthy is not just the daytime heat but also how mild the nights will be. Tuesday night into Wednesday is expected to be unusually warm, with minimum temperatures more reminiscent of a summer's night than early autumn.

Widely, overnight readings will settle between 15 and 19C. In parts of south-east England, forecasters say it is not out of the question that temperatures will fail to dip below 20C at all. Overnight temperatures in late September are typically around 7 to 11C, so this will make for a remarkably warm night by comparison.

The warm southerly winds will continue to feed northwards overnight, sustaining the elevated temperatures and preventing the sharp overnight cooling that often signals the arrival of autumn. For those sleeping without the windows closed, it may feel more like July than late September.

Meanwhile, the wider picture for the month reinforces a pattern of persistent warmth. According to the Central England Temperature record — the world's longest-running temperature series, which tracks average temperatures across a number of locations in England — the reading stood at 2.6C above normal up to 26 September.

That means September is set to become yet another month in which average temperatures come in well above normal. In fact, every month of the calendar year so far has recorded an above-average mean CET, and the year to date is running 2.6C higher than normal.

Forecasters note that it would require a sustained period of much colder-than-normal weather for the remainder of the year for 2026 to avoid ranking among the warmest years on record for the UK. Given the trajectory so far, that scenario appears increasingly unlikely.

Looking further ahead, the Met Office's latest three-month outlook, which covers October through to December, suggests higher-than-normal chances of a mild autumn and a mild start to winter. That would extend the pattern of warmth that has dominated much of the year.

For now, the immediate focus is on Tuesday's brief but pronounced burst of heat. While it will not last indefinitely, it offers a final taste of summer warmth before more typical autumnal conditions — complete with stronger winds and rain — begin to reassert themselves later in the week.

The advice for those hoping to make the most of it is straightforward: Tuesday afternoon, particularly in southern and eastern England, looks set to deliver the best of the sunshine and warmth, while those in the north and west should prepare for a breezier, cloudier day with the chance of showers.

For meteorologists, the event is a useful reminder of how air masses and wind direction can dramatically reshape the UK's weather from one day to the next, even as the calendar edges steadily towards October.