Heatwave this week by definition

Since the start of the working week, Monday 29th July, parts of the UK have been under official heatwave thresholds.

The definition of a heatwave varies globally, but in the UK is defined by the Met Office as three consecutive days with daily maximum temperatures reaching or rising above the heatwave criteria.

The heatwave criteria varies by county, ranging between 25°C and 28°C. For example, Northern Ireland's criteria is 25°C, as is large parts of Scotland, Northern England and Wales.

Dorset and the East Riding of Yorkshire's threshold is 26°C as an example, while Lincolnshire and Norfolk is 27°C. Much of London and the Home Counties however, are required to reach 28°C to warrant a heatwave.

These differences reflect the climatic differences across the UK, based on long-term averages.

Yellow Heat Health Alerts have been in place for much of England, as issued by the UKHSA, with the hottest day of the year so far recorded at the peak of the heatwave on Tuesday 30th July, as temperatures hit 32°C.

On Monday peak temperatures reached 29.6°C in Charlwood, 32°C on Tuesday in both Heathrow and Kew Gardens, followed by 31.1°C on Wednesday in Brize Norton.

Thursday could still breach heatwave threshold once again, as temperatures are forecast to reach the mid to high twenties once again for many areas.

In the days following however, temperatures will drop away, back below the heatwave thresholds.