Introduction

Temperatures across the United Kingdom are set to climb into the mid-20s as September draws to a close, offering a late-summer feel that many had begun to doubt. After a chilly start to the week, high pressure is driving a welcome warm-up that will feel familiar yet unusual for the season.

What Happened

Following a chilly start on Monday morning, sunshine and light winds allowed temperatures to rise into the low 20s across much of England and Wales. By Tuesday, the warmth intensified, with highs potentially reaching 24 or 25C in south-east England, while other regions enjoyed the low 20s. The settled conditions are driven by a building high-pressure system, which is keeping rain-bearing weather systems at bay. However, northern and western areas still saw some showers, and the week will see a gradual cooling trend mid-week. Notably, 2026 has already set records for the number of days above 25C, with last week surpassing a decades-old benchmark.

Regional conditions vary: south-east England and eastern England see the warmest, driest weather, while Wales, Northern Ireland, and Scotland experience cooler temperatures and more cloud. Rain remains likely in the north and west, but the east stays predominantly dry.

Why This Matters

This late-September warm spell is significant because it interrupts the typical autumn transition, offering summer-like temperatures just as the season changes. The Met Office defines a heatwave as temperatures reaching 26 to 28C for three consecutive days, which this period will not meet. Still, the warmth is notable for late September and could provide a much-needed boost after a prolonged period of rain. For those tracking drought conditions, the dry, sunny days in the east and south-east are helpful, though one week will not reverse longer-term deficits.

The broader implication lies in seasonal shift. Warm air transported from southern Europe or North Africa via southerly winds is still possible at this time of year, and the forecasted above-average temperatures for the last week of September suggest autumn will start with a lingering summer feel.

Key Takeaways

  • Temperatures will peak at 24-25C in the south-east, with most of the UK seeing low-20s.
  • High pressure is the engine behind the settled, dry weather.
  • The warm spell falls just short of official heatwave criteria.
  • 2026 is on track for an unusually high number of days above 25C.
  • Rain remains likely in northern and western regions, while the east stays dry.
  • Above-average temperatures are expected to continue into the last week of September.

Conclusion

While this week's warmth won't be classified as a heatwave, it's a vivid reminder that September can still deliver summer-like days. As high pressure shifts eastward and rain returns to northern areas, the south-east will hold onto the heat a little longer. Staying informed through regular forecasts will help you plan around the lingering warmth and the inevitable return to more typical autumn conditions.