Weatherwatch: When is summer?

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Snoozing in deckchairs at Weymouth beach in Dorset.
Snoozing in deckchairs at Weymouth beach in Dorset. Photograph: Kathy deWitt/Alamy

When does summer start? The Met Office says 1 June, as it defines summer as the calendar months of June, July and August. But in many northern cultures the seasons are divided by the two spring and autumn equinoxes and the summer and winter solstices. So summer occurs later than the Met Office version: starting during the period around 21 June, and ending three months later, around 22 September.

If this is the case, then why do the dictionary definitions of midsummer describe it as the middle of summer? One possible explanation is that our ancestors were more interested in the position of the sun rather than its effect on our weather. So while July and August are undoubtedly the warmest months, the longest days occur at the time of the solstice, in June.

There could be another explanation: that it is a simple linguistic misunderstanding. We usually regard the prefix "mid" as meaning "middle"; but maybe it has the same etymological origin as the word midwife – meaning "with"? Thus midsummer's day would be the first day of summer – the day the season arrives.

Nature takes no interest in the human calendar, and for our wildlife, the seasons are far more flexible. So "spring" may begin in January, as birds begin to sing in preparation for the breeding season, while signs of autumn can start in June, as the first returning migrants head south. In nature, summer hardly exists at all.

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