The "Azores high" is a semi-permanent feature of the global weather map. It is an area of high pressure, a large anticyclone which lurks, virtually immobile, in the vicinity of its eponymous islands, but which now and then in July or August extends northwards to provide Ireland and Britain with a brief glimpse of what it really would be like to have a summer.
In the days of the old sailing ships this zone of very light winds was a frequent cause of inconvenience to ancient mariners. The region became known as the "Horse Latitudes" - allegedly because any horses aboard were thrown over the side to conserve the water they would otherwise consume in a ship becalmed for an extended period. But perhaps the horse-heavers should not have been so hasty: horses, after all, have skills as predictors of the weather.
The main area of equine expertise, it seems, is rain. There are a variety of symptoms: if horses stretch out their necks and sniff the air, it portends rain; the same fate awaits us if they are restless or uneasy, or if they assemble in a corner of a field with their tails to the wind.
Not everyone believes in this, of course. Many are more inclined to the attitude of Laocoon who, having commented on the suspicious generosity of the marauding Greeks with Timeo Danaos et dona ferentis, went on to be specific. Equo ne credite ["] he warned: "Do not believe the horse."
But Sir Walter Scott in Quentin Durward gives us another version of the horse's expertise. He tells how Louis XI of France was soaked with rain after he refused to believe the prophesy of a wayside charcoal-burner. When the forecaster was asked afterwards about his methods, he gave the credit to his horse; on the approach of rain the animal invariably pricked its ears forward, walked more slowly than usual, and tried to rub its back against any wall it passed.
Horses react to the weather in other ways. They are particularly sensitive, it seems, to lightning and to thunder - even to the extent of causing themselves serious injury by bolting in a thunderstorm. When unexplained injuries occur to thoroughbreds, climatological records sometimes reveal a thunderstorm as being the likely cause.
And it was always thus; Horace seems to identify the same problem in rural Italy 2000 years ago:
namque Diespiter
Igni corusco nubila dividens
Egit equos volucremque currum.
"Jupiter, indeed, dividing up the clouds with shimmering fire, spurred on the horses and excited all the flying insects."