The Weather in the South Pacific. The Pacific: Weather. South Pacific Weather. The climate of the South Pacific islands is tropical yearround. There's a hotter, more humid period from November to April, and a cooler, drier time from May to October. The countries closer to the equator (Samoa, Tuvalu, Solomon Islands) are generally warmer than those further south (Fiji, Tonga, New Caledonia, Cook Islands).