Theoretical limit to how hard it can rain

First, the hottest temperature recorded was probably in some place like Death Valley, so the humidity was probably very low. Thus there isn't nearly as much water is the air as indicated by the saturation pressure.

Second, if you somehow did manage to have hot air fully saturated with water mix with very cold air, the hot air has much higher heat capacity (due to all the water in it). One cubic meter of -83C air has a mass of roughly 1kg, so a heat capacity of 1kJ/K. The heat of vaporization of water is about 2000kJ/kg, so by the time you'd condensed about 70g of that water, the cool air would have heated up to +55C (and that ignores the heat capacity of the hot air and the water).

So it's pretty safe to say, yes it's a limit but not a very useful limit as it is so far above what's physically possible.

1 min - 31.2mm (1.23")

60 min - 305mm (12.0")

12 hr - 1.825 m (45.0")

24 hr - 2.467 m (97.1")

72 hr - 3.929 m (154.7")

96 hr - 4.869 m (191.7")

12 month - 26.47 m (1042")

source (http://wmo.asu.edu/#global)

Almost all of the records come from La Réunion ( http://en.wikipedia.org/wiki/R%C3%A9union ), which is an island straight east of Madagascar. If you're from the US, think of the Hawaiian islands but in the Indian Ocean. Significantly, the island has peaks that rise up to 3,070 meters (10,070 ft).

I am guessing large Indian Ocean cyclones get going and then just run slap into this vertical peak in the middle of the ocean. Then, rain. Rain for apparently days straight.

Meh. I love the depth of the answer, and what an awesome visualization :D