Rain from wet moss (or other blocks)

This is inspired by dripstones. When water, either flowing or a source block, is on top of a moss block, rain should be falling from the underside of that block. This rain should do the usual things rain does - extinguish fire, including burning mobs and players, irrigate farmland, hurt endermen, blazes and striders, turn into snowfall in cold places, permit riptide, keep villagers and bees indoors, enable Axolotls to survive, and transmit conduit powers.

Making the effect dependent on water on top of the moss block would facilitate redstone-controlled rain. 

It need not necessarily be moss blocks, either. The effect could instead or additionally be given to wet sponges or foilage.