Winter Weather Forecast

A woolly bear caterpillar crossed our path Sunday…

The caterpillar was our annual reminder of folklore surrounding winter weather forecasting.

Pennsylvania Prognosticators
The Woolly Bear is nearly as famous for its winter forecast, as Punxsutawney Phil is for his spring forecast. It’s also known as the “fuzzy bear” or “woolly worm” or even the “hedgehog caterpillar” since it curls into a bristly ball when disturbed.

13 Segments
The basic belief goes that the more black there is on the caterpillar, the more severe winter weather will be in that location. With 13 weeks of winter corresponding to the 13 segments on the caterpillar, the position and number of the black bands indicates which weeks of winter will be the most severe.

“Judging by this caterpillar, early winter will be the most severe (late-December through early-January) with a final blast of winter during the ides of March”


More folklore
If the caterpillar has a heavier, very woolly coat, it will be a colder winter. Direction of travel: If a woolly bear is crawling in a southerly direction, it is trying to escape cold winter conditions to the north. If a woolly bear is crawling toward the north, it indicates a mild winter. The caterpillar in my photo was travelling northeast, so that would mean a mild winter. Once settled into a sheltered spot, the caterpillars hibernate, creating a natural organic antifreeze called glycerol.

Caterpillar to Moth
Even though there is great interest in its caterpillar stage, few people know that the caterpillar becomes an Isabella Tiger Moth.  While the wings don’t have distinctive markings, the abdomen is spotted with three longitudinal rows of small black dots. The moths are active on summer nights.

Photo: Pyrrharctia isabella – Isabella Tiger Moth (of the Woolly bear caterpillar)
By: Andy Reago & Chrissy McClarren

Late Fall forecast?
Winter doesn’t officially begin until December 21st, so what about the weather forecast for the preceding weeks? After all, our Pittsburgh area’s longstanding snowfall record of nearly 36-inches, occurred around Thanksgiving 1950. It was known as “The Big Snow of 50” or “The Storm of the Century.”

Brings back memories of flying down snow-packed streets on our Flexible Flyer sleds, at least until the cinder truck came around and put an end to the fun!


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