Residents across the Big Island face a wet conclusion to October as moderate trade winds focus clouds and showers over windward and mauka areas, with an 80 percent chance of rain hitting Hilo and Puna tonight, according to Big Island Now. A transition toward drier conditions is not expected until the tail end of a frontal boundary approaches the island chain early next week.
Current Conditions and Regional Breakdown Across the Big Island
The weather varies sharply depending on elevation and geography heading into the weekend. Hilo and Puna carry an 80 percent chance of rain tonight, with cloudy skies and occasional showers bringing lows ranging from 67 to 73 degrees near the shore and 59 to 64 degrees at the 4,000-foot level alongside northeast winds reaching up to 10 mph. Saturday brings mostly cloudy skies with numerous morning showers transitioning to scattered showers in the afternoon, with highs between 78 and 83 near the coast.
On the opposite side of the island, Kona experiences a drier forecast. Tonight brings mostly cloudy skies with scattered showers in the evening followed by partly cloudy conditions after midnight and a 50 percent chance of rain. Kona lows will settle between 70 and 76 degrees near the shore and around 60 degrees near 5,000 feet. Saturday offers a mostly sunny morning followed by a partly sunny afternoon with scattered showers and highs reaching 84 to 89 degrees near the shore.
Waimea and Kohala face identical forecasts tonight, featuring mostly cloudy skies with numerous showers in the evening and scattered showers after midnight under east winds up to 15 mph and a 70 percent chance of rain. Lows will range from 67 to 73 near the shore down to 62 to 68 near 3,000 feet. Saturday turns partly sunny with scattered showers and an east wind up to 10 mph.
The South Big Island sees mostly cloudy conditions this evening with scattered showers giving way to isolated showers after midnight, with lows near 76 at the shore and 62 at 5,000 feet under northeast winds up to 15 mph. Waikoloa remains the driest pocket on the island tonight, seeing partly cloudy skies with isolated showers and a mere 20 percent chance of rain, with lows ranging from 71 to 76 near the shore.
Tropical Moisture Brings Heavy Downpours Before Stable Trade Winds Return
Abundant tropical moisture lingering over the region will keep isolated heavy downpours possible through this evening, particularly over the Big Island where the greatest instability persists. Model soundings indicate more stable conditions developing by Friday, establishing a standard trade wind pattern through the weekend characterized by shallow passing windward and mauka showers.
A significant pattern change arrives late Sunday into Monday as an upper-level trough sweeps across the north-central Pacific. The tail end of a frontal boundary will attempt to push down the island chain, increasing windward and mauka showers before breezy northeast winds and drier air filter in behind it. This shift will drop dew points into the lower 60s on Monday and Tuesday, offering relief from current muggy conditions.
Large Northwest Swell Arrives to Bring Advisory Level Surf
Marine conditions remain active as high pressure to the north generates moderate to fresh trades. A Small Craft Advisory will likely be required for typical windier waters. An incoming north-northwest swell will bring seas exceeding 10 feet to exposed waters.
A small, short-period north-northeast swell will maintain modest surf along north-facing shores into Saturday. However, a larger, long-period northwest swell arrives late Saturday, bringing advisory-level surf to north- and west-facing shores exposed to the swell from Sunday into Monday. This swell may briefly build further on Monday before declining on Tuesday, prompting potential Marine Weather Statements due to harbor surges at Kahului and Hilo.
Fire Weather Concerns Transition to Moderate as Drier Air Arrives
Fire weather concerns remain low through Saturday due to recent rain and light to moderate trade winds. Those concerns will transition to moderate early next week as the weak front passes and brings breezy northeasterly winds and drier air to the region.
Model divergence emerges for next week regarding the GFS and ECMWF forecasts. While trade winds are projected to persist, uncertainty remains regarding their strength and moisture content. The GFS continues to hint at a tropical cyclone developing far southeast of the state, while the ECMWF does not. The National Hurricane Center is monitoring this area, maintaining a medium 40 percent chance of development over the next 7 days.
