Even without air resistance rain wouldn’t come at once.

Depending on how literally you take “no air resistance” it could mean no wind at all to no friction to slow rain.

In the first interpretation water vapour goes up straight continuously and creates layers of density proportional to the amount of sun/heat hitting the lake. Eventually the vapour reaches critical altitude and accumulates there.

Because evaporation is always happening and moves discrete particles of water randomly, there would still be particles if water coalescing into drops of rain. Think of it kind of like the same effect as raindrops hitting your windshield and combining until they get heavy enough to slide down, not a wall of water.

And in the second interpretation I hope it’s now clear that this would result in painful rain drops with high velocity, but still not a thick sheet of it.