Met Office Changes Definition of ‘Heatwave’ for the Southeast

In an attempt to properly label heatwaves as heatwaves in a world that’s warmer than ever, the Met Office has been updating the regional thresholds by which we measure them. These are being changed in advance of Summer 2022.

In the southeast, a heatwave was previously classed as any three or more subsequent days reaching highs of 27 degrees Celsius. But as temperatures creep upwards and these numbers become less unusual, the threshold number has been increased to 28 degrees Celsius. This is now the case for us in Hertfordshire and Bedfordshire, and the same change has been made for Surrey, Berkshire, Buckinghamshire, and Cambridgeshire.

Other regions have different threshold numbers, suiting the climate’s definition of what is ‘unusual’ or ‘extreme’ heat. But it’s in the southeast and central England that the rise has been most dramatic.

According to Herts Live, Dan McCarthy, head of the Met Office National Climate Information Centre, had this to say:

‘Climate statistics over time reveal an undeniable warming trend for the UK. Temperature rise has been greatest across parts of central and eastern England, where they have increased by more than 1.0C in some locations, while further north, Scotland, and areas of Northern Ireland, have seen temperatures rise by closer to 0.7C.’

He also noted that the Met Office made a study into the summer heatwave of 2018, and determined that we’re 30 times more likely to experience such extreme highs than would have been this case in 1750, before the industrial revolution. ‘As greenhouse gas concentration increase, heatwaves of similar intensity are projected to become even more frequent, perhaps occurring as regularly as every other year.’