Yesterday, the 18th of March 2018 was the coldest for that particular day in March since 1853. That’s according to the latest provisional Central England mean temperatures released from the Met Office (fig 1). The maximum for Sunday was 0.6°C and the minimum -2.2°C, and the mean of -0.8°C, was almost 6.6°C lower than the 1961-1990 long-term average of 5.8°C.
Only four other years have reported negative mean temperatures for the 18th of March (fig 2 & 3) in the daily mean CET series that started in 1772, they were 1900, 1853, 1814 and 1812.
Don’t forget that you can keep an eye on the latest daily CET values here
Looking at the observations for yesterday and the reported 06 to 18 UTC maximum temperature (fig 4), many stations across central England and Wales had sub-zero maximums, in fact at a number of stations, the temperature has remained below zero the whole weekend, which just two days from the vernal equinox is highly unusual.
I think the thermograph for the last few days from Rothamsted in Hertfordshire gives a good account of how quickly the cold snap set in last Friday, and just how cold the last 48 hours have been across the country (fig 5).