UK Set for Late September Heat Spike as Temperatures Could Reach 25C

Parts of the UK are set to experience a sharp and unusual burst of late September warmth, with temperatures potentially climbing as high as 25C on Tuesday, according to BBC Weather forecasts. The warmest conditions are expected to concentrate across south-east England, although much of England will comfortably reach into the low twenties Celsius. Elsewhere in the UK, temperatures will still be mild by seasonal standards, with the high teens expected in many areas.

This burst of warmth represents a significant departure from what would normally be expected at this time of year. Forecasters say the mercury will run roughly three to six degrees above the average for late September. To put that in perspective, typical maximum temperatures across England during this period usually sit between 16C and 19C. Tuesday's readings will therefore feel more like a continuation of summer than the early stages of autumn.

The driving force behind this temperature surge is a strong southerly airflow that will establish itself across the country as Tuesday progresses. This wind is drawing unusually hot air northwards from France and Spain, where temperatures have widely exceeded 30C in recent days. As the southerly flow strengthens, it will act as a conveyor belt, transporting some of that continental warmth directly towards the British Isles.

Across England, temperatures are expected to exceed 20C almost universally, with the highest readings reserved for the south-east, where the mid-twenties are likely. Wales, Northern Ireland and Scotland will also benefit from the milder air, with maximum temperatures on Tuesday projected to range between 17C and 22C. However, the day will not be uniformly bright, as cloudy skies and a few showers are possible during the morning before sunny spells break through over England and Wales. In northern areas, cloud cover is expected to increase as the day wears on, following a bright start.

Beyond the daytime warmth, forecasters are highlighting the unusual nature of the overnight conditions. Tuesday night into Wednesday is expected to be exceptionally mild, with minimum temperatures more reminiscent of a summer's night than early autumn. Widely, overnight lows will settle between 15C and 19C, but in parts of south-east England, it is not out of the question that temperatures will fail to drop below 20C at all. That would be a striking anomaly, given that overnight temperatures in late September typically fall to between 7C and 11C.

The southerly winds will also bring gusty conditions to some regions. Gusts of up to 50mph are expected across Northern Ireland and western Scotland, linked to a large and deep area of low pressure tracking north through the eastern Atlantic towards Iceland. That low-pressure system is helping to amplify the southerly airflow, effectively funnelling warm air towards the UK while simultaneously generating stronger winds along western coasts and hills.

The warm spell comes against a broader backdrop of persistently above-average temperatures throughout 2026. According to the Central England Temperature record, the world's longest-running temperature dataset, every single month of the calendar year so far has recorded an average mean temperature above normal. Up to 26 September, the CET is running 2.6C above the long-term average. For the year to date, the figure is also 2.6C higher than normal.

That sustained warmth means September is on track to become yet another month with well-above-average temperatures. Forecasters note that it would require a markedly colder-than-normal period over the remaining months for 2026 not to rank among the warmest years on record for the UK. The Met Office's latest three-month outlook, covering October through December, suggests higher-than-normal chances of a mild autumn and a relatively gentle start to winter.

The implications of this late-season heat extend beyond mere comfort levels. Unseasonably warm nights can affect sleep patterns and place additional strain on vulnerable groups, while sustained mild conditions may influence energy demand, agricultural cycles and seasonal ecosystems. The gusty winds accompanying the warm spell also serve as a reminder that the transition into autumn remains volatile, with spells of wind and rain expected to return later in the week.

For now, however, the focus is on a brief but notable window of warmth. The combination of strong southerly winds, imported continental heat and clear spells at times will make Tuesday feel distinctly summery across large parts of the country. Forecasters advise that while the daytime temperatures will be pleasant, the strength of the wind in western and northern areas could make conditions feel more blustery than the thermometer might suggest.

The warm episode is expected to be short-lived, with the broader pattern pointing towards a return to more unsettled and cooler conditions as the week progresses. Nevertheless, the fact that such temperatures are occurring so late in September underlines the wider trend of exceptional warmth that has defined the year so far. For many, Tuesday will offer one final taste of summer before autumn fully takes hold.