December on the Island of Hawaiʻi presents a captivating paradox. It is the heart of the local winter season, bringing a refreshing coolness and the highest likelihood of rain, yet it remains one of the most popular times to visit. This month marks a transition, where the lush, evergreen landscapes are at their most vibrant, and the powerful forces of the Pacific Ocean command attention. For anyone planning a trip, understanding the specific nuances of Big Island weather in December is the difference between a good vacation and a great one.
Temperature and General Climate Conditions
Unlike the contiguous United States, Hawaiʻi does not experience a harsh, freezing winter. December temperatures on the Big Island are remarkably moderate, especially in the most populated areas. Daytime highs in Kailua-Kona typically reach the mid to upper 80s°F (low 30s°C), while evening lows dip to a comfortable mid-60s°F (around 18-19°C). In Hilo, on the windward east side, it is noticeably cooler and more humid, with highs around 82°F (28°C) and lows in the low 70s°F (around 22°C). These stable temperatures create an ideal environment for outdoor exploration, provided you respect the microclimates that define the island.
The Rain Season and Its Impact
Precipitation Patterns and Ocean Influence
December is statistically the wettest month of the year for the island, a direct result of the Pacific storm systems that track north of the Hawaiian archipelago. These systems pump significant moisture into the atmosphere, which is then wrung out by the island’s towering mountain peaks. While this means you should absolutely pack a reliable rain jacket or umbrella, it also means the island is at its most dramatic and photogenic. The rain is often intense but brief, frequently occurring in the afternoon, followed by clear, sunny spells that wash the landscape in a brilliant, saturated green.
Windward vs. Leeward: The island’s geography creates a stark contrast. The eastern, or windward, side (Hilo) receives the majority of the rainfall. The western and western-facing slopes (Kailua-Kona) remain largely dry, basking in sunshine that feels almost desert-like in comparison.
Trade Winds: The persistent east-northeast trade winds are a defining feature of the month. They provide a natural air conditioning effect, keeping the temperatures pleasant but can also contribute to the rapid development of the afternoon showers.
Ocean Conditions and Water Temperature
For ocean lovers, December brings a mix of challenging and spectacular conditions. The summer’s calm, clear waters give way to the powerful winter swell. The north shores of the island, particularly around Waimea and the Kohala Coast, are pounded by some of the tallest surf in the world. These massive waves are a breathtaking sight from shore but make most beaches unsafe for swimming or snorkeling. Conversely, the south and west shores, such as those near Kailua-Kona, often remain relatively calm, offering excellent conditions for kayaking, snorkeling with manta rays, and diving. The average ocean temperature remains inviting, hovering around 76°F (24°C), making a light wetsuit optional for extended water activities.
Whale Watching Season
No discussion of Big Island weather in December is complete without highlighting the arrival of the humpback whales. These magnificent creatures migrate thousands of miles from the cold Alaskan waters to the warm, protected waters of the Hawaiian Islands Marine Sanctuary to breed and give birth. December marks the beginning of peak whale-watching season. While the weather is generally clear, it is common to see the spectacular sight of a spout or a breach, especially on days with good visibility. The interplay of the cool, clear air and the warm ocean creates perfect conditions for these awe-inspiring animals to be seen from shore or boat.
