You might hang jugs from tree branches, and attach cloth to each jug so that the cloth hangs down near the orchids.
Put one or more pin-holes in each jug near the bottom, so that the water drip flows onto the cloths.
Fill the jugs before the hottest part of the day, and they will keep the cloths moist until the jugs are empty. In hot moving air, the water will evaporate very fast.
Rapid air movement will blow any humidity away very quickly. I think you will need something to slow down the wind near the orchids. It might not help much to drip water onto the wind screen (outer layer) since at least half of that water will be blown away quickly.
When I wanted to shield a spot from
cold winds, I picked two trees that were close together and some small distance upwind. I wrapped a heavy tarp around one trunk and tied it in place, then extended the tarp to another tree trunk and wrapped and tied it there, so that it blocked the wind the same way a sail catches wind.
It helped that the tree trunks were at an angle to the wind, so that it was diverted with less force. If you have a fabric that is partly "open", it will slow the wind down without creating as many eddies and side winds or "whirlwinds".
You'll find that wind whips around one "sail" without being slowed much except in one small spot. , and you might have to position several sails to get calm air near the orchids. Better would be several small sections of "fence" with flexible branches or boards "woven" around posts with some open space to make several porous windscreens. Or just sections of an open lattice fence with pathways between them.
Of course, this blocks sun and walking paths as well as wind!
