Is another UK heatwave on the way in September?

Could September Bring a Sixth Heatwave to Britain?

Ninoda.com – After roughly two months without meaningful rainfall, Tuesday marked the return of unsettled conditions across much of the country. Temperatures are expected to dip by approximately 2 to 4 degrees Celsius below the mid-August norm over the coming days. Yet beneath this brief cooldown, long-range modelling points toward a return of dry, bright conditions later in the month.

A Record-Breaking Summer in the Rearview Mirror

The Met Office has indicated that 2026 is on track to become the warmest summer ever recorded in Britain. Even accounting for this week’s cooler spell, the mean temperature for the final fortnight of August would have to fall well below normal before the annual record set just twelve months ago could be avoided.

Back in June, both the Met Office and MeteoGroup — the BBC’s weather-data partners — flagged an elevated probability of above-average summer warmth and repeated heat spikes. Their seasonal outlooks weighed multiple atmospheric patterns alongside the expectation that anthropogenic climate change would tilt the odds toward hotter UK summers.

The drought’s physical footprint has been stark. At Llwyn-On reservoir in South Wales, water levels dropped so severely during the prolonged dry spell that a disused stone bridge emerged from the exposed lakebed.

Why September Could Turn Warm Again

Meteorological summer closes on 31 August. Scientists divide the calendar into four equal three-month blocks for statistical consistency, meaning the forecasts now in focus cover meteorological autumn: September, October, and November. That transitional season is inherently harder to project than the more stable summer or winter regimes.

Nevertheless, several converging signals raise the prospect of another warm episode. Computer models indicate that a high-pressure system may anchor itself south of the British Isles during the opening weeks of September. At this time of year, such a ridge typically delivers dry, predominantly sunny conditions and can funnel additional warmth northward from continental Europe.

Soil moisture remains critically low. July proved the driest month on record across England and Wales, and more than two-thirds of England together with the entirety of Wales currently sit under drought classification. When ground is parched, incoming solar energy is not consumed by evaporating residual moisture; instead it feeds directly into heating the overlying air, accelerating temperature spikes. This week’s showers, while welcome, are insufficient to re-saturate the soil or meaningfully alter the drought trajectory.

Marine conditions compound the picture. Sea-surface temperatures encircling England and Wales are running up to 3 °C above their climatological norms. That surplus of oceanic heat acts as a thermal reservoir, sustaining elevated air temperatures onshore even when winds shift direction.

What the Official Outlook Says

The Met Office’s long-range projection for the autumn quarter assigns a probability of a warm three-month period that is

“higher than normal.”

The agency further warns of an

“increased risk of heatwaves and heat-related impacts, especially during the first half of the period.”

With September still roughly two weeks distant, no specific date or duration can be assigned to any potential warm spell. What can be stated with confidence is that the risk envelope is open.

The same long-range outlook also projects an autumn that is likely drier than average. The Environment Agency has noted that

“weeks of above average rainfall”

would be required to relieve the prevailing drought, and no indication of such a sustained wet period appears on the immediate horizon.