31st May 1944 was another very warm day over much of the UK and Ireland. Temperatures reach 87F at Croydon with 70 to 80F widely reported elsewhere.

A trough to the west of Ireland pushed slowly east, triggering thundery showers in SWEngland & Wales. A huge 60mm of rain fell at Aberporth in west Wales between 7am and 6pm.

Note the low over southern Greenland, continuing to highlight the risk of more unsettled conditions ahead.
It was on the evening of 31st May 1944 that Chief Meteorologist, Group Captain James Stagg attempted to bring together the disparate forecasts for the following week for presentation to Commanders.

At this stage the forecasters on the eastern side of the Atlantic were in broad agreement with thoughts of more unsettled weather, whilst American forecasters held out for a ridge of high pressure building and hence fairer weather for the anticipated D-Day date of 5th June.

Stagg was facing some very tough decisions!

(Orginal charts (C) Crown Copyright 1944 National Meteorlogical Archive & Library)