Powers of the poor man’s weatherglass

The scarlet pimpernel always knows when it will rain.
The scarlet pimpernel always knows when it will rain.

Given the reliability of today’s forecasts, none of us should be caught out by the weather. But however much we intend to pay attention those forecasts seem to induce a trance-like state, so that when they end we are none the wiser.

However, last week was easy to predict. As Charles II is supposed to have said, “The English summer is three fine days and a thunderstorm”. Now, after that record-breaking heatwave, we’re back to will-it-or-won’t-it. Fortunately, folklore has plenty of natural signs that warn of rain.

Helpful summertime sayings include: “Dew falling by night, the next day will be bright”, or “Summer mist at dawn, the next day will be warm.” Also, less cheerfully, “Rain from the east, lasts three days at least.”

Some flowers and grasses react to levels of humidity in the air, making them useful predictors of rain. Grass chooses a fine, dry day to disperse its pollen so when sufferers from hay fever are having a bad day, at least it will be a fine one.

No honeybees in your garden today? This points to a downpour, as they won’t leave the hive if it’s going to be wet. Bumblebees don’t seem quite so fussy — they’ll hide under a leaf during a shower. Midges bouncing happily in the evening air mean the next day will be fine, but if they decide to bite you then rain is on the 

For its forecasting powers, nothing could beat the scarlet pimpernel. This native wild plant has such responsive flowers that it used to be called the poor man’s weatherglass, or shepherd’s barometer. Its shy flowers open when the sun shines, and close at once when rain is on the way. The only drawback is its habit of closing up anyway in the afternoon, rain or shine, so it is only useful until around 3pm.

The scarlet pimpernel flowers until late August. A creeping annual, it grows on dry field edges and waste places. Herbalists employed it to treat skin and eye problems, among many other ailments: “No heart can think, no tongue can tell, the virtues of the pimpernel.”

Wet blanket

The best-known forecaster of summer rain has to be St Swithin, a bishop of Winchester who died in 862. A humble man, he had asked to be buried in the minster yard so that “the sweet rain of heaven might fall upon my grave”. When he was canonised the monks, ignoring Swithin’s last request, decided to move him to a fine shrine indoors. On the day of the exhumation — July 15 — the saint showed his disapproval with a heavy downpour. Forty days of rain and floods followed.

We shouldn’t fuss too much over the number because in legend, forty was commonly used to mean “a long time”. However, the saint’s warning is no empty threat — around mid-July our weather does tend to get stuck in a rut. If it’s unsettled then, that’s how it will continue for the rest of the summer. This also means the saint can predict a drought: “St Swithin’s Day, if ye be fair, for forty days ‘twill rain nae mair.”