How does a wooly worm caterpillar affect the weather?

The wooly worm does not affect weather. They are indicators of weather because they are hardly ever seen in warm months such as July or June. We always see them in fall in a hurry to get somewhere. They are going into hibernation. So when you see a wooly worm headed somewhere during a month such as October or November that means cold temperatures are coming.

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People look for the intensity of the black color on the banded caterpillars, that are black and brown, or they compare the ratio of the black to brown coloration on the bodies of the caterpillars. If there is more brown than black, they predict it will be a milder winter, and, if there is more black than brown, there will be a very harsh winter.