Monsoons.

Monsoons can be the darnndest things. You can't always tell when you
get up in the morning what the day might be like. It might be a
beautifull morning. Not a cloud in the sky. Not a cloud on the
weather radar, but pretty soon, the hot air rises and hits the cold
air aloft, then seemingly, out of nowhere, the clouds begin to build,
turn black, then the sprinkles start. Next, all hell breaks loose,
the lightning flashes, the rain starts to pour out of the sky like the
floodgates have been opened. Water everywhere, running like a river
all over the place. You never know when, but when the temps get over
85, and there is a bit of humidity. There it is.