I'm not sure it matters what part of the country you are in. Barring climates way to cold for them, snakes don't just crawl into places for the heck of it, they go where the food is - or where it smells like food MIGHT be.
My property is on the Mason Dixon line (not some tropical / desert place) and within the last week I came face to face with 2 big black snakes right near where the TT it usually parked (at the dealer now). One under the lawnmower and another on the shed door handle. With trees / downed logs, tall grass / weeds, rocks, and outbuildings all with mice / voles and such around - We have snakes aplenty. One crawled out of the chimney inside the house this week - wife snapped a pic and sent it to me showing his head peaking out of the flue cover.
I'm not saying they will get into just about anything, just that they follow the food (mice). We are newbies to the TT world and I will be trying seal up as many potential entry points as possible to keep ALL critters out.