there are many different thoughts about the moisture going from cold to hot or hot to cold.
My thought is that the moisture comes from the air circulating against metal that is a different temperature. I seal my barrel with saran wrap and a rubber band and rub a small amount of beeswax on the 209 and use Teflon plumbers tape on the BP threads.
I hunt or have hunted many different parts of the country and Canada and I have had to wipe off the out side of the guns when moisture beaded on them. But have never had a problem with ignition.
P.S. I keep a fired 209 to seal it when in car or building.