All else being equal, what happens if you're hunting in a woods stand, situated between a field in one direction and a creek in the woods on the other?
Depends on the size of the creek, flow, and water temp. If it's a dry creek bed then it isn't going to move the air. If it's a cold spring fed, flowing stream then it'll absolutely suck wind into it.
I was sitting on the porch of my parents' cabin yesterday morning watching the sun come up. Zero wind but as the warm morning sun heated up the ground as its beams crept up the hollow, there was a fairly stiff breeze pushing up into the head of the hollow. My dad pointed out that the canopy wasn't moving. The tops of the trees were dead still. The wind was only rushing across the ground as it warmed up. That's thermals.
As for flat ground, BSK nailed it. If you're not on a field edge there's probably not much to worry about. In the morning as the ground warms up, the air rises. In the evening it falls. The trickiest I've ever experienced on flat ground was a 30 acre island of mature timber in the middle of a huge cattle pasture. I learned to only go in after sun up and as long as I could get in a tree undetected I was fine. Deer would be all around me & never know the better. But it's impossible to hunt it in the evening. Doesn't matter which tree I'm in or where the deer are. If they enter the woodlot as the sun is dropping, I'm busted. It's like a pool that contains all of my stink. No exaggeration I could hear deer sorting from 100yds upwind of me. First time or two I dismissed it as they were spooked by something else but eventually I realized it was me. When evening thermals dropped, those cool dark woods contained every bit of my stink. Once I quit hunting it in the evenings and only after sun up mornings, I began doing really well. I still don't understand exactly what's going on in there in the evening but the deer sure seem to know it. Thermals can be weird. Every spot is unique.