We were at the south rim for the first few days of November.
I would suggest that you save your legs and (if you are under 200lbs) let the mules do the work !!? ;D
Unfortunately, Im a couple of lbs over weight so we had to rely on the great bus service to tour the rim instead.
We were going to walk a 1 mile stretch of "unpaved" track at the top of the rim - until we found it was around 2 feet away from the edge, with no rail and a straight drop down.
When walking away from the trail, I slipped on the gravel and fell over. Im glad we weren't on that trail !!
Whilst we were there, we saw an air ambulance come to collect someone.
Ann-Marie commented that it would cost a fortune to get airlifted from the Grand Canyon - and if they ever needed to air lift me from there, did I think they would fly over a couple of times for her to take a few pics !! (she's like that? :'().
Anyway, whilst we were there, the weather was great - nice and warm by 11am and then cooling off from around 5pm
Paul