Phew! What a scorcher!

By Stephen Burt

These were typical newspaper headlines earlier this week. So how did we fare in Reading?

We did set one extraordinary record during this short-lived hot spell. We have daily temperature records for the university back to 1908, and as well as maximum and minimum temperatures these include the air temperature observed at 0900 UTC (10 a.m. in British Summer Time). Until Wednesday, the hottest morning on our records was Sunday 10 August 2003, when the 0900 UTC temperature stood at 28.4 °C. That particular day went on to become the hottest day on Reading’s long record, when the temperature rose to 36.4 °C later that afternoon.

On Wednesday morning, our principal observer Mike Stroud could hardly believe his eyes when the dry-bulb thermometer at 0900 UTC stood at 30.6 °C, by more than 2 degC the hottest morning in Reading in more than a century.

Fortunately or unfortunately – depending upon your viewpoint – extensive cirrus and altocumulus then largely obscured the Sun for the next couple of hours, and the temperature fell back to 29 °C, before rising quite late in the afternoon to the day’s maximum of 33.6 °C. This is of course by Reading’s standards a very hot day, but it ranked only fifth in the hottest July days on record (incidentally, displacing the hottest day of the legendary 1976 summer in doing so) … and it failed to make the ‘Top Ten’ hottest days since our records commenced. Had the rise in temperature from 0900 UTC to day’s maximum been more typical of previous heatwaves, we could well have broken the August 2003 record, and just possibly surpassed 38 °C.

Only a little further east, the cloud cover during the morning was less thick, and this led to a pronounced east-west gradient in maximum temperature. A new UK July record was set at London’s Heathrow Airport at 1413 UTC when the temperature reached 36.7 °C, just surpassing the previous record of 36.5 °C set at the RHS Gardens in Wisley, Surrey, only nine years ago on 19 July 2006. Further west along the Thames Valley, 34.9 °C was attained in Maidenhead, 33.6 °C in Wokingham and here at the University, 32.7 °C at CEH Wallingford and 32.3 °C at Stratfield Mortimer, between Reading and Basingstoke.

Some Met Office climatological stations report only once per month, so it may yet transpire when the returns arrive that somewhere was even hotter than Heathrow. A few locations are already known to have established all-time records last Wednesday, eclipsing the many notable heatwaves of recent years – we can include the summers of 1976, 1983, 1989, 1990, 1995, 2003 and 2006.

What was all the more surprising was that Wednesday’s great heat was only the second day this year to have surpassed 25 °C. It will be interesting to see what the rest of the summer brings – more hot weather, or was Wednesday our ration of summer for this year?

For more on notable heatwaves in Reading over the last century or so, including tables of the hottest days in each month and the ‘Top Ten’ for the whole record, see the newly-published One hundred years of Reading weather.

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