Several Big Island rain gauges break records for lowest October rainfall as drought worsens

Records for the lowest October rainfall were broken at several East Hawai‘i locations as the normally wet windward slopes of the Big Island were especially dry last month, with most sites posting totals at less than 20% of average.

According to the National Weather Service, drought — which is already affecting the entire Big Island to varying degrees — is expected to develop or persist during the next 3 months throughout the entire state.

Ongoing El Niño conditions also will likely result in below-normal precipitation for the main Hawaiian Islands well into 2024.

Most rain gauges on the Big Island saw below-average rainfall in October.

The rain gauge at Hilo International Airport recorded just 1.36 inches of rain in October. Its average is 10.24 inches for the month. The record is particularly notable because it’s the least amount of rain recorded in October by the gauge since 1949.

The Hakalau, Kahuā Ranch, Ka‘ūpūlehu, Keaumo and Mauna Loa Observatory gauges had their lowest October rainfall totals in more than a decade.

Records for lowest rainfall also were broken last month at Glenwood, Pāhoa Beacon, Pi‘ihonua and Waiākea Uka.

The highest monthly total of 5.25 inches was recorded at Pāhala and Kapāpala Ranch, which was 99% and 103% of the average, respectively. Kapāpala Ranch also had the highest daily rainfall total of 1.01 inches on Oct 23.

Rainfall totals for 2023 through the end of October were near to below average at most Big Island rain gauges. The U.S. Geological Survey gage at Honoli‘i Stream had the highest year-to-date total of 152.98 inches, or 81% of the average.

For all rainfall totals around the Big Island in October, click here. For year-to-date rainfall totals, click here.

October’s dry conditions caused a significant increase in drought intensity throughout the state.

At the end of October, more than 75% of the islands were experiencing severe or extreme drought. As of Oct. 10, that included ‘Upolu Point, South Point, Ka‘ū and the leeward slopes of Maunakea.

Even moderate drought covered more than half the main Hawaiian Islands, including the remaining areas of the Big Island.

For more details about the drought, see the National Weather Service’s latest Drought Information Statement.

Overall, the weather pattern over the main Hawaiian Islands during October looked more like something from mid-winter as opposed to what would be expected in early fall.

Strong low-pressure systems in the North Pacific pushed the low-level high-pressure ridge southward to just north or even directly over the state resulting in most days having a stable air mass and light winds, with land and sea breezes dominating local wind conditions.

There were three weak cold fronts that reached at least a portion of the main islands, none of which made it to the Big Island.

Notably, the first — which moved over Kauaʻi on Oct. 4 before dissipating Oct. 5 over the Kauaʻi Channel — was also the first cold front passage for the 2023-24 west season and was earlier than normal by a couple of weeks.

The only other noteworthy rain event occurred along the windward slopes of O‘ahu’s Ko‘olau Range during the evening of Oct. 3 under a large-scale light wind pattern.