After a few days -- or maybe right away!-- you may realize that it never gets cool in Samoa. The afternoon rain is like a warm shower, and indeed the downburst are just as strong sometimes. The normal temperature range is 75-85 degrees and that includes the rain.
The are two places to get cool, in the deep ocean water off the reef or in a shaded mountain waterfall.
There are several trails, some official through the park system, and some jsut old paths everybody knows about.
A walk up Matafao Mountain can end in a waterfall over black volcanic rock into a cool pool.
Picture is Amalau Valley falls, Tutuila, national park