28°C hot?

Courtesy BBC

So Matt Taylor reckons the definition of hot is a maximum temperatures of 28°C. Hot seems to have undergone a redefinition in recent years, perhaps because by the same logic that’s behind the move to rebrand global warming global heating. As you know I am great believer in temperature anomalies and I reckon that an anomaly of 10°C above the LTA for that day is a pretty good definition of hot and if it you get three consecutive days a heatwave. As the mean temperature for the old London weather centre is 22.4°C in June, a hot day in my book would be a temperature of 32°C in the capital, and not 27°C or 28°C, and even the 28°C forecast for Birmingham with a lower mean June temperature of 19.0°C doesn’t quite cut it. The thing is with no strict definition for the term ‘hot’ in forecasts where do we go when temperatures reach 32°C? Very Hot? An what happens when they reach 35°C? Exceptionally hot? Or as is promised could happen in the not too distant future 40°C? There’s no doubt it will be a very warm weekend across inland parts of England and Wales but not really hot.
One bit of guidance I did come across was in a very old publication from the Met Office library called the ‘Weather Map’ from 1955. The values are in Fahrenheit but at least do give some indication that hot is 11 – 14°F above normal. So the 22.6°C at LWC would be ~73°F. Adding the 11°F to it would mean that hot would be >=84°F or >=28.9°C.

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