Anorak News | July 1 2015 was the hottest day on record for jets at Heathrow Airport

July 1 2015 was the hottest day on record for jets at Heathrow Airport

by | 12th, July 2015

According to the Met Office, 1 July 2015 was the “warmest July day since records began”. The record was set at Heathrow Airport “when the temperature reached 36.7 °C at 3.13pm. The previous highest July temperature was 36.5 °C on 19 July 2006 in Wisley, Surrey.”

Hot, then. But was it really a record?

Mark McCarthy, Manager of the Met Office National Climate Information Centre discusses records and how we record them.

He states:


1 July 2015 has the honour of holding the highest recorded temperature for a July day with 36.7 °C at Heathrow.


What do we know about Heathrow?

On 1 July the maximum temperature recorded at Heathrow (36.7 °C) was higher than Kew (35.7 °C).

Kew and Heathrow are around 8 miles apart.

Modern instrumentation means we can look at the temperatures minute-by-minute at the two sites, as shown below. The two locations recorded very similar temperatures through most of the afternoon and the average temperature at the two sites between 12:00 and 18:00 GMT agree to within 0.02 °C. However, there was a peak in temperature at Heathrow between 14:00 and 14:30 GMT that was not seen at Kew Gardens. 

We get to see a graph.


hottest day on record



We can see the sudden spike in temperature, which led to that record-breaking peak.

Why did it spike? And why didn’t it spike in Kew? The Met Office says is clould be down to cloud cover.

But we don’t get to see where the weather recording technology is stationed.

Paul Honewood wonders:

1) Just how meaningful is a temperature recorded at a major international airport? As somebody pointed out, why not count the 40C+ measured in the oven at Wimbledon?

2) According to the Met Office’s own hourly data, the maximum temperature reached at Heathrow was 35.9C, well below the record claimed. This was at 15.00, and by 16.00 the temperature had declined considerably.

Has the temperature really climbed so much in a matter of minutes, or are we simply seeing the temperature peaks resulting from airport traffic, exaggerated by subtle wind shifts.

Christopher Brooker:

For a start, it was odd for the Met Office to base its claimed record of 36.7C (98F) on a single reading at Heathrow airport, when it is well-known that thermometers surrounded by a vast area of tarmac can exaggerate heat by as much as 2 degrees. Even the Met Office’s own hourly record only showed its highest Heathrow reading on Wednesday as 35.9C, while four other sites nearby showed the day’s hottest recording at just 35C.

It was hot. But was it so hot that records tumbled?

Posted: 12th, July 2015 | In: Reviews Comment | TrackBack | Permalink