A day in the heat may have no effect on the film, but you should hand carry pro films on board the plane, because cargo holds become quite hot at the tropical airports. Because of the low light levels in the rain forest, you may want to consider a tripod or monopod. But before you pack one in your luggage and then pack it up the volcano, try mounting your camera on it in the pouring rain and taking pictures. A tripod may not be worth the aggravation, and you may want a faster film in spite of the graininess. If you choose to bring a tripod or monopod, be sure you try it out in the rain before you go.
Some designs collect water in the legs.
Aside from the extra weight of the water, you don't want to drain the 'pod inadvertently onto your camera, film, and other items in your formerly dry pack. The Civilized Explorer .