By Philip Eden

The English summer, it has been said, consists of two fine days and a thunderstorm. This assertion is normally attributed to George II, although Richard Inwards' volume, Weather Lore, perhaps wisely regards its originator as anonymous.

Whatever its genesis, this view is probably nearer the mark than the more romantic image of high summer weather in Britain - long, hot, hazy days in the sun, crowded beaches, parched gardens, and so on. The summer months do from time to time comprise a succession of days of blazing sunshine and soaring temperatures, but these years are rare enough to become imprinted on the community memory - 1900, 1911, 1921, 1959, 1976, 1983, 1990 and 1995, for instance.

Just as infrequently, the summer contains no extended settled spell at all and only a few days when the warmth of the sun allows us to shed the ubiquitous mackintosh. The last time this happened was in 2007. Between these two extremes we can find most of the summers we experience in Britain, usually containing one or two of those short heat-waves followed by thunderstorms - we are experiencing one now - with plenty of indifferent weather between.

Professor Hubert Lamb, one of Britain's best-known climate experts, analysed weather patterns over 100 years to determine whether any particular patterns tended to recur at certain times. While acknowledging that our weather varies widely from year to year, Lamb did succeed in determining several recurrent themes which he called "singularities". It was important to explain why these climatic preferences happened at specific times of the year, rather than regard them as mere statistical quirks, and this he was able to do as well. Nevertheless, he emphasised that his singularities were not regular enough nor reliable enough to be used as a forecasting tool.

Lamb dubbed the period mid to late-June the 'return of the westerlies' and mid to late-July 'thundery and cyclonic'. After several months, from February to early-June, when winds from a westerly quarter are conspicuous by their absence, they return with a vengeance around mid-June. In late-May westerly winds blow in only 15 per cent of years, but by June 20 the frequency has increased to 52 per cent. During July, the frequency of westerlies declines slightly to about 40 per cent while cyclonic weather types become more frequent, reaching a peak of 35 per cent by the end of the month.

© Philip Eden