I live and hunt in Texas, snakes are just part of the equation unfortunately. One of the biggest rattlers I’ve encountered( and killed) in the field was end of November/ beginning of December. It was fairly cool out. We had 3” of snow on the ground the week before where I killed her. They do in fact come out of their dens during the winter months with weather permitting.
I am a firm believer in snake avoidance- I’ve been practicing it for 30 yrs with my bird dogs- it works! Never had one bit cause they were messing with a snake. In fact, the dogs get a little sideways, do a weird point, freeze with a high head etc etc which to me is great because it’s all the warning I need!! We usually just walk around it and keep hunting! I just did snake avoidance with a dog last week- this young female is very zippy and forward moving. I didn’t want to chance it. We had 2 rattlers out - she winded both of them before we got her to them. She didn’t want anything to do with either one.