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The new normal?
Heatwaves show the difficulty of assessing extreme weather events in a changing climate, write ROX MIDDLETON, LIAM SHAW and JOEL HELLEWELL
The sun sets in Chesterton, Warwickshire, amid the heatwave in 2020

AT THE end of March the Met Office announced that it was increasing the heatwave threshold for eight English counties by one degree Celsius. It attributed this change to increasing global temperatures due to climate change.

A heatwave is defined as at least three consecutive days with maximum temperatures meeting or exceeding a threshold. 

Within Britain, the exact threshold varies across the counties due to their different average temperatures. Counties with higher average temperatures will have a higher threshold required for a heatwave to be declared. 

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