Tag Archives: UK temperature record

40C in London end of July? Probably not

The long range weather models are causing much excitement on various forums with one run predicting an anomaly of +16C on Sunday, July 29th.

july29th

Such an anomaly would see temperatures exceed 40C in London, unprecedented looking back at records to 1841; the highest temperature recorded in the UK was 38.5C at Brogdale, near Faversham, Kent, in Augut 2003.

Though it is improbable it is not impossible. Back in April conditions allowed the temperature to rocket to a monthly record of 29.1C, a positive anomaly of 15.5C!
A repeat of similar synoptic conditions would be needed – these would obviously be helped by the record meteorological drought conditions this area is currently experiencing.

Because reliable thermometer records of heatwaves only go back as far as 1840 it is impossible to quantify whether 40C has ever been exceeded in the UK prior to then.

However, accounts of the heatwave of July 1808 suggest parts of England may have come close. Far removed from images of freezing Georgian winters and miserable summers the July of 205 years ago was among the warmest ever. The monthly mean for July 1808, according to the Central England Temperature series, was 18.4C – the 6th hottest July since the beginning of the series in 1659.

Luke Howard, the ‘father of meteorology’ who at the time lived in Plaistow, referred to the heatwave in his diary on July 13th: “Temperature at 9am 84F. The intense heat of the maximum lasted nearly three hours till about 4pm. At 6pm the temperature was 90F.” Another entry mentions a reading taken nearby. “Another at Plashet, a mile and a half eastward, indicated 96F as the maximum under the shade of a house.”

While Howard’s methods of measuring the temperature ran short of modern standards, his thermometer was hung under a laurel bush, the values still give a valid insight into the heatwave.

Tales of the heatwave, which particularly affected east and north-east England, can be seen in letters sent to local newspapers around the country. Many describe labourers dying from heat exhaustion while working in fields. Farm animals and horses suffered a similar fate.

One letter from Hull, published in the Coventry Mercury, said: “At Sigglesthorne, the honey in some beehives melted, ran out upon the ground, and most of the bees drowned in it. At Sutton, a lamb and a dog belonging to the Rev Mr Croft of Rowley, expired in the heat; and several birds dropped down dead, while flying over the streets of this town.”
Of course it is impossible to know about the health of people and animals that died but that birds dropped out the sky suggests extreme heat.

 

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50 years of London heatwaves

Ask a dozen people what they think is a heatwave in this country and you’ll probably get 12 different answers.

The view across to St Paul's Cathedral from Bankside at low tide by Scott Whitehead
The view across to St Paul’s from Bankside at low tide.

The UK press is always keen to tell us that a ‘heatwave is on the way’ – even if it is March and the heatwave in question brings temperatures no greater than the high teens Celsius.

Although in the UK there is no official definition of a heatwave the World Meteorological Organization description is “when the daily maximum temperature on more than five consecutive days exceeds the average maximum temperature by 5 °C, the normal period being 1961-1990”. In other words that March heatwave would see the thermometer peak higher than 15.3C five days in a row. Pleasant enough – but no big deal.

The Met Office, working with the Department of Health, provides a ‘Heat-Health Watch System’ for England which is triggered when a threshold temperature in the South East is  31 °C by day and 16 °C overnight for at least two consecutive days.

I have vague memories of the weeks of sunshine in 1976 but the hot spells that stick in my mind the most are August 1990, when the UK temperature record was set in Cheltenham, Gloucestershire, and August 2003 when an 8-day hot spell saw the all-time UK temperature record broken when 38.5C was reached at Brogdale, near Faversham, Kent.

eggs on roadLast July, when compared with the previous summers, saw some of the best  summer weather since 2006. But where does last year compare with the good summers of 2003, 1995, 1990 and 1976? I decided to have a look back at the daily records for this area which stretch back to 1959.

I have drawn up a list of all days back to 1959 that have an average mean daily temperature of 23.5C or higher. This shows that there has been 93 such days. However, to qualify for the Met Office’s Heat-Health Watch System – ie two days like this in a row the list narrows. To make my job easier, I have narrowed the list further to 3 consecutive days where the mean has been 23.5C or higher. Though I loathe really hot weather in my experience I can put up with it for a couple of days. It is only when it gets to the third day of hot, sleepless nights that it starts becoming unbearable.

In terms of intensity and hours of sunshine, 2003 comes out on top. Though many people will argue that 1976 is more impressive -that summer, which comes in second, only produced two spells that satisfy my criteria. The first heatwave saw temperatures soar above 31C for six consecutive days from June 23. The start of the second, on July 3, saw Bjorn Borg win the first of five Wimbledon mens’ titles as he prevailed over Ilie Nastase in 35C heat.

The summer of 1995, which saw my driest-ever August with just 0.7mm of rainfall all month, comes in 3rd, with six days of mean temperatures of 23.5C or higher.

Polo advert for the heatwave that coincided with the  Queen Mother's birthday in 1990
Polo advert for the heatwave that coincided with the Queen Mother’s birthday in 1990

Looking at the data another way, ranking the average total daily mean temperature of each spell, sees 2003 again come out 1st, with August 1990 and July 1983, 2nd and 3rd. Looking back through history it is not really surprising that 2003 comes out on top. While  it was hot in London the heatwave across the Channel contributed to the death of over 70,000 people throughout Europe, France being the most affected.

This weekend promises to be very warm and sunny but it will pale into insignificance compared with the hot spells of the past. The mean temperature on Saturday and Sunday is unlikely to exceed 17C. heatwave table