If it is 70degF or higher out, it doesn't chill your muscles ... And I don't know about you but soaking heavy leg warmers don't exactly help me much when it is cold either. The best thing is a thick coat of petroleum jelly on your naked legs (at least for races and rides where you KNOW you will get wet).
Assuming that there is no wind, and the road is wet, it it easier to move than on a dry road? I do not know why, but I seem to think that the answer is yes for some strange reason.
i've often wondered the same thing, but never thought to ask about it here. but i definitely have noticed that over the years and seasons. i ride all year round, wet or dry, and it feels easier to me on wet days. i thought it was less friction with the road.