Rubber boots cause one's feet to sweat on long walks thus socks will move about and you can get blisters which can have a negative effect on hunting for the next few days.
It is not severely cold on the Spring hunts, I usually do a lot of walking and when it is cold it warms up as the morning goes on. I favor a pair of light weight hiking ankle top boots which are water proof. I purchased a pair of Rocky's in 1996 and still wear them today.....They have a lot of miles on them. They are not exactly water proof anymore with a couple a small holes at the top of the toes. I would like to get another pair.
One of the coldest foot Spring turkey hunts I had was a morning I waded into through high wet grass with hiking shoes which were not waterproof and set all morning.