A high pressure in the Iceland/Greenland region delivered cool but dry weather types to most of the UK between the 4th and 18th, but the anticyclone receded sufficiently to allow mainly cyclonic conditions over the British Isles from the 19th till the 28th. The noticeable factor of the month was the total sunshine for the May was 230.4 hours, and Lyneham experienced some maximum temperatures that were extremely different from the remainder of the month. On the 27th Lyneham experienced it's warmest day of the year so far, temperatures peaking 26.5°C and the same evening temperatures did not fall below 13.3°C, making it the warmest night for over a year. Twenty four hours later the minimum temperature for the night was freezing at 0°C, the plants certainly had a shock.

Two weeks earlier, a high pressure cell drifted east across the UK between the 10th and 12th, the showery activity diminished, most areas had prolonged sunshine by day, but nights were frosty. The sun was out for over half the day, experiencing over 12.6 hours of sunshine, however the temperature only reached 15°C during the day and the clear skies meant the temperature dropped to 4.2°C. The winter months have seen remarkably low rainfall and again May 2005 was quite a dry month, only 45.8mm of rain fell. Having said that, over 85% over the month precipitation fell between the 19th and 24th May.