UK Braces for Unseasonable 25C Heat as Late September Warm Spell Grips Britain

Parts of the United Kingdom are set to experience a remarkable surge in temperatures on Tuesday, with the mercury potentially climbing as high as 25C in what forecasters describe as a burst of late September warmth. The unseasonably hot conditions will be driven by a strong southerly airflow that is drawing exceptionally warm air northward from the continent, bringing a taste of summer to a month that is typically associated with the onset of autumn.

According to Simon King, Lead Weather Presenter, the warmest locations will be concentrated across the south-east of England, where temperatures are expected to reach into the mid-20s Celsius. However, the warmth will not be confined to that region alone, as temperatures will widely reach into the 20s Celsius across much of England, while other parts of the country will see the high teens. This represents a significant departure from the seasonal norm, with temperatures running around 3 to 6 degrees above the average for this time of year.

The primary driver behind this unusual warmth is a strong southerly airflow that is developing as Tuesday progresses. Unusually hot air has been sitting across France and Spain, where temperatures have widely been in excess of 30C in recent days. The southerly wind will act as a conveyor belt, transporting some of this continental warmth northward to the UK. This weather pattern is not uncommon in late September, but the intensity of the warmth makes it noteworthy.

Across England, temperatures will exceed 20C widely, with the highest readings expected in the south-east, where the mercury could climb into the mid-20s Celsius. To put this into perspective, average temperatures across England in late September typically range between 16 and 19C. The forecast high of 25C would therefore represent a significant anomaly, more characteristic of a warm summer's day than the early days of autumn.

The morning across England and Wales may begin with a good deal of cloud and a few scattered showers. However, as the day progresses, sunny spells are expected to develop, allowing temperatures to rise steadily. This combination of sunshine and warm southerly winds will create conditions that many will find pleasantly surprising for late September, offering an opportunity to enjoy the outdoors before the colder months set in.

While the south-east will experience the highest temperatures, the warmth will also be felt across Wales, Northern Ireland and Scotland, where maximum temperatures on Tuesday are expected to range between 17 and 22C. These regions will start the day with sunny conditions, but cloud cover will increase as the day wears on. Despite the cloud, temperatures will remain above average, continuing the theme of unseasonable warmth that has characterised much of the month.

The southerly winds are expected to strengthen throughout the day, with gusts of up to 50mph anticipated in Northern Ireland and western Scotland. This blustery weather is linked to a large and deep area of low pressure that is moving north in the eastern Atlantic toward Iceland. The interaction between this low-pressure system and the warm southerly airflow is what is driving both the elevated temperatures and the strong winds, creating a mixed bag of weather conditions across the country.

Tuesday night will also prove to be unusually warm, with temperatures in some locations not falling much below 20C. The warm southerly winds will continue overnight into Wednesday, meaning that minimum temperatures will be more typical of a summer's night than early autumn. Widely, overnight temperatures will range between 15 and 19C, but in parts of south-east England, it is not out of the question that temperatures will remain above 20C throughout the night. Overnight temperatures in late September are typically around 7 to 11C, so this will make for an exceptionally warm night.

The persistence of the warmth overnight is particularly notable because it reflects the strength of the southerly airflow and the lack of any significant cooling influence. In typical autumn conditions, clear skies and longer nights allow temperatures to drop considerably, but the combination of cloud cover, warm air advection and brisk winds will prevent any significant cooling. This could have implications for those who find it difficult to sleep in warm conditions, as well as for energy consumption patterns.

September is on track to become another month where average temperatures come in well above normal. According to data from the Central England Temperature (CET) record, which is the world's longest-running temperature record and tracks the average temperature across various locations in England, the mean temperature up to 26 September is 2.6C above normal. This continues a pattern that has been evident throughout the year.

Every month of this calendar year has seen the average mean CET above average, and the year to date is running 2.6C higher than normal. This remarkable consistency suggests that 2026 is likely to be one of the warmest years on record for the UK. For that not to be the case, temperatures would need to be much colder than normal during the remaining months of the year, which appears increasingly unlikely given the current outlook.

The Met Office's latest three-month outlook, which covers October through December, suggests higher-than-normal chances of a mild autumn and start to winter. This would continue the pattern of above-average temperatures that has persisted throughout 2026. While mild conditions may be welcome to some, they also raise broader questions about the changing climate and the increasing frequency of temperature anomalies.

The warm spell is expected to be relatively short-lived, with conditions likely to change as the week progresses. The strong southerly winds and the associated low-pressure system will eventually give way to more typical autumnal conditions, bringing wind and rain back to the UK. However, the brief burst of warmth serves as a reminder of the variability of British weather and the influence of large-scale atmospheric patterns.

For now, residents across much of the UK can look forward to a day of unseasonable warmth, with the south-east enjoying the highest temperatures. Whether this late September heat is a welcome reprieve or a sign of things to come, it is a notable weather event that underscores the dynamic nature of the UK's climate. As September draws to a close, it seems the month is determined to go out on a warm note.