August had some of everything except snow


View towards London from Coopersale on a showery late August day (Roger Emmens)   

August had some of everything except snow!

We might not have had all four seasons in a single month, but it certainly seemed like three, in a month of great contrasts.

The first half of August was building up the heat, followed by a prolonged period with torrential downpours, so much so that the location of the weather station was flooded, which knocked out the power supply from 14:19 on Sunday 16th August until 14:43 on Wednesday 19th August, and meant we lost more than three days of readings. Consequently we don’t know just how wet it was during Sunday's thunderstorms nor those on Monday and Tuesday.

At the start of the month, it was very warm, and that soon became hot. We had six successive days with the maximum temperature over 30°C, the second time this has been recorded after July 2006. We also recorded our 7th and 8th ‘tropical nights’ (nights where the temperature never falls below 20°C) and for the first time on two nights in succession, on 11th and 12th. *

This heatwave then broke in spectacular fashion, with seven successive days of storms, frequently thundery, from Thursday 13th to Wednesday 19th. When floods knocked out our power on the afternoon of Sunday 16th, we had already recorded 22.2mm of rain that day, so the final total was substantially more. We actually recorded 62.6mm in the three or so days we were operational in that period, but anecdotally reports of containers left outside with 150mm or more of rain accumulating in them give an indication of the extent of the downpours.

Consequently, the recorded month total of rain, 94.8mm, could be understated by anything up to double that. Even so, the recorded amount places August 2020 as our sixth wettest August, and if we had recorded just another 30mm it would have been our wettest ever August, beating 2010. It seems likely therefore that August 2020 was indeed our wettest ever, but sadly we can’t prove that.

The remainder of the month then became relatively cool and cloudy, and culminated in a couple of very early named storms: Ellen and Francis brought strong winds and more downpours, and Storm Francis during 25th and 26th delivering a maximum gust of 29mph, or Beaufort Force 6, unusually strong for August.

The temperatures dropped too, and the 29th gave a day maximum of just 14.1°C, our fifth coolest August day maximum, whilst the overnight period 30th-31st yielded a minimum of 7.7°C, our seventh coolest recorded August minimum.

So this astonishing month variation from highest to lowest temperature of 28.6°C is comfortably our greatest ever monthly temperature range. A spectacular month of variable weather indeed!

* Based on data for 1979 - 2013

Below is the summary data for August 2020 (except for the period 14:19 on Sunday 16th August until 14:43 on Wednesday 19th August due to flooding knocking out the power supply).

MeasureUnitMinimumAverageMaximumAverage minAverage maxTotal
Absolute humidityg/kg6.09.715.6
Relative humidity%257098
Temperature°C7.717.936.314.122.8
Wind source°4196359
Wind direction°0150359
Wind strengthmph0320
Rain daily accumulationmm0.03.122.294.8
Barometric pressuremm997.7948.21022.6
Solar irradiancehPa0141970
UV indexW/m²0.01.07.8
Cloud base altitudem356133000
Dew point°C6.114.220.7
Heat index142336
Wind chill°C7.72039.9

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