UK to reach 26°C next week as heat dome pushes warm air northward

The UK is forecast to experience a warm spell next week, with temperatures in the south-east reaching up to 26°C—potentially warmer than Athens, which is forecast to remain below 24°C. The warm weather is being driven by high pressure building across the country and warmer air being drawn northward from the continental and subtropical Atlantic as a deep low-pressure system develops west of the UK. Most areas will experience above-average temperatures for late September, with Tuesday expected to be the warmest day of the week across southern England.

The duration and geographic extent of the warm spell vary by region. Southern areas of England and Wales are forecast to remain mostly dry and warm throughout the week, while Scotland and Northern Ireland may see the warmer period cut short by a cold front moving in from the west, which could bring rain and unsettled conditions midweek. The Met Office has indicated that "the prospect of one final heatwave before the end of the month is certainly not out of the question," though current forecasts do not meet formal heatwave criteria. In contrast, Netweather forecasters have stated there is "no sign" of a late September heatwave at present, expecting temperatures in the low to mid-20s rather than heatwave conditions.

2026 has already been a record-breaking year for warm days. By mid-September, the UK had exceeded 89 days above 25°C, surpassing the previous record of 89 days set in 1959. This follows the UK's hottest summer on record, with June, July, and August averaging 16.5°C. Earlier in September, a similar heat dome affected mainland Europe, bringing temperatures exceeding 40°C in parts of Spain and Portugal.

The warm and dry conditions present a challenge for water management. Reservoir and water storage levels remain critically low across much of the UK. The Environment Agency has warned the country will need above-average rainfall throughout autumn and winter for most areas to exit drought status by April 2027. Environment Agency chief executive Philip Duffy stated the drought situation "remains very serious," noting that "several reservoirs are concerningly low." Recent rainfall has fallen well short of seasonal requirements—by mid-September, locations such as Leconfield in East Yorkshire had received only 11% of normal September rainfall, and Durham just 14%, compared to the typical 50–60% by this point in the month.

Meteorologically, the warm spell is generated by a heat dome—a large area of high pressure that causes air to sink and warm through compression while suppressing cloud formation. Beyond next week, forecasters indicate that more unsettled conditions may return from the Atlantic, with longer-term projections showing conditions becoming changeable with spells of rain and temperatures returning to near normal. Some forecasts also reference a developing El Niño event in the tropical Pacific, which could bring wetter and stormier conditions to the UK in subsequent months.