A tall rubber eyecup, the kind that extends above the eye lens all around, not only blocks stray light while you're observing but acts as a miniature dewcap when you're looking away. The same principle works on large scales. The tree is a giant dewcap, and it can work for you too. If you'll be looking at only one part of the sky, it's nice to have trees around and behind you. Not just your telescope but your charts and accessories will stay dry longer.
Trees also reduce wind problems, but a slight breeze is a good thing.
Radiational cooling is slow and inefficient compared to heat transfer with the surrounding air, so even the mildest breeze will keep your telescope nearly up to air temperature. The Heat is On There will be times and places where none of this is enough. You then have no choice but to warm your optics, usually electrically. A 120-volt hair dryer, used gently from a distance so it doesn't overheat the glass and warp it, will blow off dew for perhaps five minutes. Then you have to use it again.