Geez, Layne - how would the blankets of mold be able to stay all healthy and luxuriant at that level?
Jon's information is what I remember reading, too. One thing that I learned while painting some rockets outdoors last year was that humidity levels can vary quite a bit in a small local area. For instance, if you have a grassy lawn, or an extensive bed of shrubbery or plantings, you really don't want to do your spray painting while you are standing on your lawn or near your shrubs. You will find drier conditions if you go over to your driveway (assuming that it has dried from any recent rain) or out to the street to spray that coat of paint onto your model. Going to a larger paved area, like a parking lot, is even better. The idea is that where there is a lot of vegetation, there is more humidity, because the plants and the millions of little beasties that live among them, as living things, release or exhale water vapor continuously. Blades of grass and little bugs may seem to be too small to really affect local conditions by very much, but when there is a concentration of hundreds of thousands of them, such as in a patch of lawn, they make a real difference, especially for the first few feet above the ground. And if there is a body of water nearby, such as a pond or a swimming pool, it will send the humidity level soaring in the area right around it.
Gravel driveways can actually be quite moist, too; the gravel actually helps to retain moisture. And if you are near a freshly plowed field or any place where there has been some digging, forget it. Any time the topsoil is broken or turned over, it releases tons of moisture into the air.
For similar reasons, spray painting at the beach is probably not a good idea, either.
MarkII