Coming in late, as usual on this subject....In colder conditions, I
generally start out with a rump rug, then roll it up once I think my horse is
adequately warmed up. If it's raining, I leave it down. If I'm going
to be doing an extended stretch of walking I put it down. I also put it
down as I come into a check. I have three...one heavy weight, polarfleece
with waterproof cover, one with just a light "net" lining and waterproof cover,
and one lightweight wool for summer mornings that start out a little cool.
I have learned to keep my horse covered if it's even a little bit cool or breezy
at a check. In this respect I feel they are similar to humans, and I know
that even if I'm warm when I'm exercising, I get chilled quickly when I
stop.