Wanderlust World Wanderlust World Because the Pacific Ocean spans half the planet—from the Arctic to the Antarctic—there is no single "December weather." However, broad patterns dominate the tropical and subtropical zones where most maritime activity occurs.
In December, the tropical Pacific is warm. Surface temperatures generally range from the mid-70s to mid-80s °F (24–29 °C). The warmest pool sits in the western Pacific near the equator (the "Western Pacific Warm Pool"), while the eastern Pacific off South America runs cooler due to upwelling—though this flips during El Niño events.
The dominant surface winds are the northeast and southeast trade winds, blowing steadily from the subtropical highs toward the equator (east to west). In December, these trades are typically robust, averaging 15–20 knots across the central and western basin, creating consistent swells and favorable sailing conditions for westbound passages.
December marks the start of the Southern Hemisphere cyclone season (running through April). The Southwest Pacific (Coral Sea, Fiji, Vanuatu, New Caledonia) and South Indian Ocean see the first named storms. In the Northern Hemisphere, the typhoon season is winding down, though late-season storms can still form in the western North Pacific (Philippines, Guam). The eastern North Pacific hurricane season officially ends November 30.
Long-term data show Pacific sea surface temperatures have risen ~1 °C (1.8 °F) since the late 19th century. This warming fuels more intense tropical cyclones, alters trade wind strength, shifts rainfall patterns, and accelerates sea-level rise—impacts already observed across Pacific island nations.
Mariners and travelers should always consult real-time forecasts—conditions vary wildly across 60 million square miles.