After a sunny start to Sunday the cloud built up ahead of the cold front advancing from the west, which obscured the sun just after midday and produced light rain that amounted to 2.1mm. The first shower began just before 14.30 and the second at 17.25.
A cooler day than on Saturday but still above average from the last of the warm air originating in Iberia, which lifted the thermometer to a maximum of 22.3C early in the day at 10.58, before the cloud increased.
The effect of the cold front could be felt overnight with a below average temperature as the thermometer fell away to a minimum of 8.2C in the early hours at 04.06, Monday.
The new day on Monday initially saw very bright conditions but variable cloud then blocked any sunshine, with the thermometer recovering to 11.8C at 08.00 in almost still conditions.
Weather report for May and Spring 2019
It was a cool May with the mean temperature just below average. The statistics show that although the daytime temperatures were in fact above average they were offset by the many cold nights that meant the mean minimum was 1.1C below average. There was only one air frost, -1.2C on the 5th, but several nights gave a ground frost with no evidence above ground, especially during the early days of May.
Warm air brought to us on a south-westerly air flow from Iberia meant a warmer end to the month with the warmest night on the 31st with a minimum of 13.9C, which was 6.8C above the 35-year average.
Although the last month of Spring was below average, the season was warmer than normal (+0.8C) with a mean of 9.71C. It is interesting to analyse the data since my station began recording in 1984 and find that Spring of that year was exceptionally cold with a mean of 6.83C. Investigating the statistics for that year I found that March was 2.1C below average, April 1.1C lower than average and May a significant 2.2C below the current average. By contrast, the Spring of 2011 produced a mean of 10.51C, the warmest from my records.
For that particularly cold Spring of 1984, hard frosts occurred on the 2nd and 4th of April with the thermometer falling to -6.0 and -5.0C. This followed a cold March that produced 11 air frosts, the coldest of which was -3.5C on the 29th.
Contrasting 1984 with the warmest Spring in 2011, although a hard air frost measuring -6.3C was recorded on 8th March 2011, no air frost occurred after 26th March or for the whole of April and May.
Although the examples above cover the past 35 years, the graph for this period shows an almost continuous rise in the mean temperature with the exception of the cold Springs in 1996 and 2013.
Rainfall in May 2018 was concentrated on three days, the 7th – 9th, when over half the month’s precipitation fell and 6.2mm, 14.4mm and 14.0mm respectively was recorded. The total rainfall for the month almost equalled the average with 59.5mm when the average is 61.0mm. There were only 6 days classified as wet days when the precipitation was equal to or greater than 1mm and 21 dry days in May.
The trend of drier than average rainfall continues into 2019. The rainfall for 2018 was 62mm below the 35-year average with 783mm. The first five months of 2019 have produced a total of 301mm a deficit of 55mm compared to the 35-year average. However, set against that figure must be the loss through evaporation from ground sources and plant life, the equivalent rainfall of 237mm.
The River Kennet, just below its source where it rises at at Winterbourne Monckton, dried up on Thursday 30th May.
The year of 2018 was not the driest I have recorded, as that occurred in 1996 with 594mm of precipitation, whereas six years later, in the very wet year of 2002, 1146mm was recorded.