Maui rainfall remains below average in September, National Weather Service reports

The National Weather Service’s monthly rainfall summary for September shows Maui County continuing a below-average rainfall trend, with only a few locations on the Haleakalā slopes nearing or surpassing average rainfall totals.

Most rain gauges across Maui recorded subpar totals for another month, extending the island’s ongoing dry pattern. Several gauges were unavailable in September due to maintenance, but available data confirm that the driest conditions persisted in Central Valley and leeward West Maui. Despite the continued dryness, rainfall percentages relative to the long-term September averages were generally higher than those recorded in August.

The US Geological Survey’s Puʻu Kukui gauge recorded Maui’s highest monthly total at 6.18 inches—just 28% of its long-term average—and also logged the island’s highest single-day total of 2.18 inches on Sept. 11. Meanwhile, the Kulani National Wildlife Refuge gauge reported its driest September since its records began 14 years ago.

Year-to-date totals across Maui have remained relatively steady, with most sites maintaining 60% or more of their typical rainfall levels. Leeward areas and the central valley, however, continue to lag behind, at roughly 50% to 60% of the year-to-date norms. Even with a dip in September, the West Wailuaiki Stream gauge retains the highest cumulative total in the county at 112.91 inches, about 66% of its year-to-date average.

Molokaʻi and Lānaʻi conditions

On Molokaʻi, rainfall was also below average, especially in leeward areas, which continue to rank among the driest locations in the state. Like Maui, September totals showed a modest improvement compared to August’s particularly dry figures. Lānaʻi followed a similar pattern, ending the month with totals that remained under seasonal averages despite isolated light showers.

Statewide rainfall overview

September opened with lingering moisture from a mid-level low that produced enhanced showers on the 1st, mainly affecting Kauaʻi and the Big Island’s Kona district, where totals topped 3 inches in some spots. Maui saw relatively modest rainfall that day.

From Sept. 8–11, deep tropical moisture associated with the remnants of former Tropical Cyclone Kiko moved across the islands, producing widespread light to moderate rainfall. Windward areas of Maui and the Big Island recorded some of the heaviest amounts—1 to 2 inches—on the 11th.

Later in the month, an upper low and weakening front brought a round of enhanced showers from Sept. 18–22, particularly over the western half of the state. Maui experienced limited benefit from that system, with the heaviest rain concentrated farther west.

Toward month’s end, fluctuating wind patterns led to scattered light showers driven by local sea breezes, while Kauaʻi stood out as the wettest island statewide, receiving up to 3 inches in interior areas by Sept. 26.

Although September totals improved slightly from August, the NWS noted that many parts of the state remain significantly below their long-term rainfall averages for the year to date.