Make peanut brittle only on sunny days

[snopes]

Comment: Is it true that in order for your peanut brittle to turn out you
need to make it on a sunny day?

[geminilee]

I would say that is probably right. Humidity can really effect candy making. Not just brittle, either, but taffy, or even hard candies. While you could probably find a way to compensate for the extra moisture, it may just be easier to wait until it is not raining.