In the Philippines, there are two seasons -- tag-araw (sunny) and tag-ulan (rainy) -- and it's interesting that I almost never run games when it's raining.
I used to, back when I ran Cyberpunk and it was almost a given that the setting was an acid-rain soaked city. But a rainy jungle is almost non-existent in my repertoire.
Perhaps when I run Fading Suns or Enigmundia I shall have a rainy season based campaign. Hunting for monsters in the rain, especially at night, adds an extra level of difficulty.
For people traveling, the salakot is a good option. It's a waterproof hat, like a flattened cone, that keeps rain off your head and -- unless the wind is almost horizontal -- out of your face as well. Of course, a typhoon-strength wind will rip it off your head. The hood is fine (if it's waterproof) but is best with some sort of cap or hat to keep the edge of the hood from sagging into your eyes. You want your hands free to hold weapons and gear, not constantly adjusting your hood.
Another concern is footware -- if your feet are wet and cold, you're not happy!
The images are from a comic book that I wrote and scripted, and a friend -- Gener Pedrina -- did the art and lettering for.