Clear evidence of climate warming – a summary of the weather of May 2024

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The Aurora put on an impressive display – here near Epping (photo: Isabel Tyler)

Clear evidence of climate warming

A summary of the weather of May 2024

The most striking weather event of May was actually in the realm of solar weather: the stunning Aurora Borealis that lit up our skies in May. We were lucky to have clear skies at the crucial time in an otherwise duller than average month!

Back on Earth, we can now report that May 2024 was the ninth successive month in which both temperature and rainfall were above the long term average for the month. To put that into context, if the variability of both these parameters above or below the average was random, then probability of that is about 4 in a million, or around once every 20,000 years.

Temperature first: May 2024 had no really prolonged warm spells, although the top temperature of the month of 25.6°C on 9th was above the long term average, yet the average daily maximum of 19.0°C was the fourth warmest on record. However the overall monthly mean of 14.2°C equalled the warmest May (1989) of our 40 years of records, and the lowest temperature of the month, 5.8°C, and the average daily minimum, 10.0°C, were both the highest on record.

As for the rain, it kept on coming! With 92.8mm, it was the seventh wettest May in our records, coming in at 165% of the long term average for May of 56.1mm. The wettest day was 2nd when 24.0mm fell, our 6th wettest May day. Overall it rained on 14 days, which is exactly average.

On to the barometric pressure, and it is no surprise with all the wet that the mean pressure for the month of 1011.7 hPa is below the long term average, which stands at 1015.2 hPa; yet the month’s low was 998.3 hPa – almost exactly average – which came unsurprisingly when the depression that delivered our wettest day passed through, and the high was 1029.3 hPa – above average.

The winds in May were generally gentle: the maximum gust was on the last day of the month and clocked 24mph (Force 5), the third lowest in our records (which for barometer and winds cover just 16 years). The average daily maximum was 14.8mph, which is the lowest on record for May. The commonest wind direction in May was unusually from the east.

MeasureUnitMinimumAverageMaximumAverage minAverage maxTotal
Relative humidity%468095
Temperature°C5.814.225.610.019.0
Wind source (most common/highest gust)SectorENW
Wind speedmph2.32414.8
Rain daily accumulationmm3.024.092.8
Barometric pressurehPa998.31011.71029.3
Solar irradiance during daylightW/m²2571190779
Sunshine (sunny if irradiance > 120 W/m2)Hours9.512.5295

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