September heatwave? What the latest UK weather forecast really says

The UK could be in for another taste of summer this weekend, but forecasters are warning against calling it a September heatwave.

Temperatures are expected to climb sharply across southern and southeastern England on Sunday, with highs of around 28°C to 29°C and a chance of 30°C in the hottest spots. That would make for an unusually warm start to September, particularly after a summer that has already produced exceptional temperatures.

Yet the weather story is far from uniform. While parts of southern Britain could enjoy sunshine and near-30°C temperatures, Scotland, Northern Ireland and parts of northern England are set for much cooler and windier conditions.

The latest Met Office forecast describes Sunday as very warm, followed by a return to cooler conditions.

UK weather forecast: How hot will Sunday get?

The biggest temperature rise is expected across southern and southeastern England.

The Met Office forecast indicates that temperatures could reach about 28°C or 29°C in parts of the south, with 30°C possible locally. London and the southeast are expected to see particularly warm conditions, with sunny spells helping temperatures climb.

The warmth will not cover the whole country.

Northern Scotland, Northern Ireland and parts of northern England are expected to remain much cooler, with brisk winds and temperatures closer to 19°C or 20°C in some locations. Rain will also affect northern and western areas as weather systems move across the country.

That creates a striking north-south divide: summer-like conditions for parts of southern England while other parts of Britain experience something much closer to early autumn.

Is there actually a September heatwave?

Not officially.

The expected warm spell is too short to meet the UK’s heatwave definition. The Met Office defines a heatwave as at least three consecutive days where maximum temperatures meet or exceed the heatwave threshold for a particular location. Those thresholds vary across the UK.

Sunday could bring temperatures that feel unusually hot for September, but the warmth is not currently expected to persist for long enough to qualify.

The distinction matters because headlines about a “September heatwave” can make a brief warm spell sound like a prolonged period of extreme heat.

The latest forecast points to temperatures falling again after Sunday’s warmth, with cooler and more unsettled conditions returning.

Why are temperatures rising again in September?

The brief surge in temperatures is linked to the movement of high pressure and warmer air from continental Europe.

High pressure positioned south of the UK is shifting eastwards, helping draw warmer air towards France and southern Britain. The setup is expected to give southern areas a short-lived boost in temperatures.

The effect is much weaker farther north, where low pressure and stronger winds will dominate the weather pattern.

That is why two very different forecasts can exist within the same country on Sunday.

READ ALSO

UK heatwave finally set to end as Met Office forecasts rain across Britain next week

Could the UK hit 30°C in September?

Yes, 30°C is possible in parts of southern and southeastern England on Sunday.

If temperatures reach the 30s, it would add another remarkable statistic to an already extraordinary year for UK weather. ITV Weather reported that reaching 30°C in five different months of the year has not happened since 1947.

In 1947, the UK’s temperature reached 34.4°C. In 2026, temperatures have already exceeded 38°C on two occasions.

That makes Sunday’s potential 30°C reading less significant because of the number itself and more interesting because of where it sits within the wider pattern of the year.

2026 has already rewritten the UK’s heat records

The September warmth comes after an exceptional summer.

The Met Office said on September 1 that summer 2026 was provisionally the UK’s hottest summer on record, with an average mean temperature of 16.5°C. The series used by the Met Office stretches back to 1884.

The agency said the summer was also among the sunniest on record in some locations and unusually dry for many areas. It linked the increasing frequency of temperature records to human-induced climate change.

That context makes another late-season warm spell particularly notable.

It does not mean that every warm day should be treated as another heatwave. Weather patterns can produce short periods of unusually high temperatures without creating the sustained conditions needed for an official heatwave.

What will the weather be like after Sunday?

The warm spell looks short-lived.

The Met Office expects temperatures to turn cooler after Sunday, with unsettled conditions developing during the following days. Rain is expected to spread southeastwards, with western Scotland among the wetter areas, while showers could become heavy or thundery in places.

The outlook for September 8 to 17 points towards a fairly unsettled period, with showers and longer spells of rain affecting many areas. Northern and western parts of the UK are expected to see more frequent rain, while southern and eastern areas have a better chance of longer dry periods.

Temperatures during that period are expected to be broadly near average.

There is some hope for warmer and more settled conditions later in September, but confidence becomes lower at that range. The Met Office currently sees the possibility of more settled weather developing around the middle of the month, potentially bringing drier conditions and some warmer days.

Why this weekend’s weather could be misleading

Sunday could feel like summer has returned, particularly in London, southeast England and surrounding areas.

But the wider forecast tells a different story.

A warm Sunday followed by cooler, wetter and windier weather is not the same pattern as the prolonged heat seen during major UK heatwaves. The country’s regional differences are also important: people in southern England may experience temperatures approaching 30°C while those farther north deal with conditions nearly 10 degrees cooler.

The safest reading of the current forecast is that Britain is getting a brief September warm spell, not a nationwide heatwave.

That distinction could become even more important as September progresses. Forecast confidence naturally falls the farther ahead meteorologists look, meaning predictions of a major late-September heatwave should be treated cautiously unless the signal strengthens in shorter-range forecasts.

Frequently asked questions about the September UK heatwave

Will the UK have a heatwave in September 2026?

There is no official UK heatwave forecast for the current warm spell. Temperatures may approach 30°C in southern and southeastern England on Sunday, but the hot conditions are not expected to last long enough to meet the heatwave definition.

Will the UK reach 30°C this weekend?

30°C is possible in parts of southern and southeastern England on Sunday. Forecast temperatures are expected to reach around 28°C to 29°C in many of the warmest areas.

Which parts of the UK will be hottest on Sunday?

Southern and southeastern England are expected to record the highest temperatures. London and surrounding areas are among the locations expected to experience very warm conditions.

Will Scotland be hot on Sunday?

Not across most of the country. Northern Scotland is expected to be much cooler and windier, with rain also affecting parts of the north and west.

Is 30°C unusual for September in the UK?

Temperatures around 30°C can occur in September, so the temperature itself is not unprecedented. What makes the current forecast notable is the wider context of an exceptionally warm 2026 and the possibility of reaching 30°C after months of unusually high temperatures.

Will September 2026 be hotter than normal?

The latest longer-range forecast suggests temperatures could be slightly above average initially in the latter part of September, before moving closer to average. Confidence is lower farther into the month.

When will the UK weather turn cooler?

The warmest conditions are expected around Sunday, with cooler weather developing afterwards. Rain, showers and stronger winds are expected to become more prominent during the following days.

Could there be another heatwave later in September?

A warmer spell later in September cannot be ruled out, but there is not enough forecast confidence to describe one as a likely heatwave at this stage. The Met Office’s longer-range outlook currently points towards a mixture of settled and unsettled conditions.