Well, searched before posting and found the answer to my question in a deluge of 'Rain' threads...
The only creative thing that I can add to this is, the other day there was a slight rain starting, hardly more than a drizzle. I was outside working, and noticed that the chickens all ran into their coop.
'Strange', I thought... 'birds are so strange.'
A minute later, the thunderstorm struck and I hastened inside as well. Not strange; but smart.
Next time I'll watch the chickens. Not as dumb as one would think; standing in the rain isn't so dumb anyway. Both I and my daughter love it (only my wife thinks that someday we may catch cold; hasn't happened yet but it is sure to happen someday and being out in the rain will surely have been the cause).
I prefer to think that we're developing brown fat cells, as we like to stay outside a lot when it freezes over. I wonder if Chickens have brown fat...