Comment by dkarl

Weighing down the leaves is one possibility, but is it also possible that water adhering to surfaces was creating reflections and providing alternative paths for the signal? I don't know if such a thing could happen at that frequency, but if you imagine looking out a window at night towards a window in a distant building, with a tree blocking the direct line of sight, and someone in the window sending you a message with a flashlight, you would only see the light via reflections. On a dry night the reflections might be matte and hard to see, but on a rain-soaked night you might be able to see stronger and sharper reflections on metal poles, walls, or puddles that were visible from both windows.