It’s slightly difficult to gauge the number of heatwaves in Central England. One of the reasons for that is the CETCET Central England Temperature series is made up of a composite temperature from three separate sites, the other is that the series extend back so far, 1878 in this case, that choosing a fixed value for the whole of the last 145 years is problematic because of increases due to global warming. My DCET application allows the user to define which threshold to use and it’s length. In the example above the application displays all heatwaves of three consecutive days or longer, with maximum daily temperatures of 25°C or higher. The UKMOUKMO The Meteorological Office is the United Kingdom's national weather service. It is an executive agency and trading fund of the Department for Business, Energy and Industrial Strategy current criteria for heatwaves is 25°C for a large part of the UKUK The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and Northern Ireland.. Of the three sites that are used to calculate a composite temperature for central England at the moment, one of them Stonyhurst is in the 25°C region, the main one Rothamsted, is in the 28°C region, and the other Pershore, is in the 27°C region. So you could argue I should use the weighted average of the three 27°C but what the hell.
The longest heatwave in Central England lasted for 16 days, from the 23rd of June to the 8th of July 1976. That’s one day longer than the 15 days of 2018 for similar dates. The earliest heatwave in the series back to 1878 if I’ve done my programming correctly was from the three days from the 28th to the 30th of May 1944. The latest heatwave was the three days that started on the 29th of September and lasted to the 1st of October 2011.
I’ve catalogued 145 individual heatwaves in 145 years which is a bit of a coincidence and not a lot of people know that.
The recent record breaking heatwave for September (2023) that’s just finished (and here I’m assuming it finished on the 10th) lasted for seven days from the 4th to the 10th of September, which makes it the joint fifth longest heatwave in the series to date, in fact it equals the seven day heatwave that occurred earlier in the year in June.
Are heatwaves getting more common?
Yes, of course heatwaves are getting more common, CET temperatures have been rising at the rate of 0.254°C per decade for the last 50 years, so they are bound to get more frequent and longer lasting. The chart below gives you an idea of the increase, it displays a bar chart of the annual number of days when daily maximum CET exceeds 25°C. I have added a 10 year centred average to the chart, and also a linear trend from 1878 to 2023. A shorter trend would show a much larger rise than the 0.4 days/decade increase than this trend shows but I am starting to flag and it’s getting near to dinner.
