Rain
Right click the link to the sample below, choose "Save target as ..." and save it with your other sounds.
Depending where you are on the Disc, it may rain sometimes. When it does, you get wet (and hear the squelch sound if you've set it up already). To avoid getting too wet you had better spot that it is raining. With this example you can now hear the rain so you won't fail to spot that you are standing in it. It is a 10 second sound sample and will trigger as you enter any location where it is raining. This means that it may continue for a few seconds after you get out of the rain, but who cares? It also means that it will stop after 10 seconds of standing in the rain in one location. That's not the point though. At least you heard it raining. The pool of Pishe in the Temple of Small Gods is a location where it always rains if you want to test this out.
The bit saying "It is a" at the start of the trigger always starts weather descriptions so this helps to cut down on accidental triggering of the sound.
Follow the same pattern as door sounds to set this up (you have done the tutorial haven't you?) or cut and paste one of your existing door sound triggers and just modify the trigger and the sample.
Updated 18/10/03 - added asterisk to start of Trigger definition just in case any rogue text spills on to start of line.