Ticks are dormant in the leaf litter....when I fall hunted in December and January I treated my clothes with perminone....more than once I got ticks on me after warning up the ground for several hours in 30 degree weather.
It seems that 30 degrees is right about the cutoff point for tick activity. I don't think I've ever found one crawling on me any (or much) below that. I know I've found them crawling when it was a lot colder than you'd expect to find one.
