Is a September heatwave forecast for the UK?

The UK is bracing for a heatwave this weekend, with temperatures set to climb to summerlike levels in some areas. Sunny spells and heavy rain are expected, with the warmth persisting into Monday but cooler conditions arriving by midweek. Computer weather models predict a mixed picture for the latter half of September, but there are no definitive signs of a heatwave just yet.

Rain outbreaks are forecast to spread southwards on Saturday, clearing from Scotland and Northern Ireland but continuing into parts of northern England, Wales, and the Midlands, potentially bringing thunder and lightning. Southern England should remain largely dry with sunny intervals and warm and humid temperatures in the mid-20s Celsius.

Sunday could see rain lingering in southern England, but a dry afternoon is expected for much of the UK. The northern half of the country may see slightly cooler temperatures, while parts of Wales, the Midlands, and southern England could reach highs of 23-25C. Monday could be even warmer, with temperatures reaching 22-26C across England and Wales, and 20C in parts of Scotland and Northern Ireland.

However, these temperatures are still below the criteria for a heatwave, which would require three consecutive days above a temperature threshold varying by region. Unsettled weather with low pressure areas and the jet stream is expected to bring spells of rain and brisk winds over the next week. While wet weather may be welcome for drought-stricken areas, high pressure could bring longer dry interludes and above-average daytime temperatures later in the month. Long-range forecasting remains uncertain, but there is currently no indication of a heatwave.