My thanks to Michael Adam, a bee keeper for contributing to the discussion about the relationship between bees and weather. After reading the page on Weather Lore on this site, he sent me this:
“Regarding the bee-crowding saying under your weather signs – Probably partially true. Bees crowd around the entrance of the hive for many reasons, but most spectacularly when it is extremely hot and moist. They need to dehydrate their honey before they cap it to reduce the moisture content, otherwise it will ferment in the comb. Also, being unable to regulate their own internal temperature, they must rely on the air to cool off. Taking those two factors into consideration, it is best on extremely warm days to hang out outside the hive (we call it “bearding”), so the combined heat from the weather and normal hive activity (even during the winter the inside of a hive can be warm and moist) doesn’t bake the larva that are inside or soften the wax. Also, clearing out space helps increase airflow to aid the cooling process and to dehydrate the honey. Bees will even line up and fan their wings to encourage drafts.
So is the weather necessarily nice if they do this? Well, it is hot out, that’s for sure. I have had bees do this just before and during sudden thunderstorms, late into the night, on beautiful days, on cloudy days, etc.
If they aren’t bearding, it just means that they are going about their daily activity because the conditions inside the hive aren’t too hot or moist.
If this just refers to smaller clumps “lollygagging” around the entrance in larger numbers than usual..there are many reasons why this might happen, and probably can’t be used to predict weather with any accuracy. Yes, it probably means it’s a nice day out, but usually when it is nice, the bees are busy working. You could probably get a better estimate of the weather by watching how many trips are being made away from the hive. On a nice day, it looks like an insanely busy airport.”
There is a little more about bees and weather in The Walker’s Guide to Outdoor Clues & Signs.
Image credit: http://freemasonry.bcy.ca/images_download/beehive.gif