Warm May Of 1917

[Weather-history]

After virtually 5 months of sustained cold which began in December 1916, May 1917 was overall a very warm month with a CET of 12.8C

Even during this month, some low minima were reported with 28F on the 3rd and 22F on the 7th at West Linton. Other low minima recorded on the 7th of May include 25F at Bawtry and 26F at West Witton.

The 2nd half of the month was very warm with maxima of 79F at Bawtry and Regent's Park on the 28th and 80F at Camden Square also on the 28th.

The mean temperature at Camden Square was 59.1F (+5.1F)

Bonacina's account of a thunderstorm on the 29th of May 1917

"On May 29th, I happened to be at Potter's Bar and during the heat of the afternoon, observed a growing tendency towards the formation of thundery cumulo-form clouds. About 4.30pm, I noticed that the summits of some of the cumulus banks were turning into false cirrus - a sure indication of storminess. A preliminary storm had already broken over London and catching the 4.55 train to King's Cross I soon noticed that the independent centres of cumulus clouds were coalescing into a deep thunder mass with the preciptation of huge drops of rain. I reached Hampstead about 6pm just in time for the commencement of the main storm which lasted an hour. During this hour, a dense storm sheet of terrible blackness moved stealthily over the high ground of Hampstead Heath from NW to SE, discharging to the ground a series of dangerous but magnificent forked flashes followed in at least 3 cases by instantaneous crashes of the most alarming, explosion-like character. At the same time, a surface current from a southerly direction was moving up to the cloud level -- to judge from the contrary motion of lower scud. After the storm had ceased about 7pm, the warm moist atmosphere was fraught with the delicious fragrance of May blossoms and the clearing sky revealed, high above the receding thunder clouds, an exceptionally delicate and beautiful structure of cirrocumulus at first in soft small flakes, afterwards in well-remarked ripples having a pearly lustre."

[Terminal Moraine]

The fact that caught my attention in this interesting piece was Bonacina's reference to the scent of May blossom after the storm. An indication of how cold the spring of 1917 had been when the Hawthorn is still in flower in north London on May 29th as this is about the average date of first flowering of that species at 350m a.s.l around here.