Much of Oahu was getting hit by up to 2 inches of rain an hour Monday and another area of heavy rain is set to move through in the coming hours, which could see rainfall reaching 3 inches an hour.
“Rain events of this size can cause catastrophic flooding and affect areas that do not usually flood,” according to the NWS.
Low spots are subject to extreme runoff, which can clog bridges and culverts, exacerbating the already dangerous flooding. Landslides are also expected.
The declaration allows the use of funds “to support state and county efforts in providing quick and efficient relief of suffering, damage, and losses caused by flooding and other effects of heavy rains,” Ige said on Twitter.
The days-long rain event had already left some communities saturated.
Nene Cabin on the Big Island topped the list at 14.07 inches in 48 hours as of Monday night. Keaumo, also on the Big Island, recorded 13.64 inches and Kula on Maui received 12.95 inches.
While the rain is creating potentially hazardous conditions, it may also help Hawaii recover from a drought.
More than half of the state, 56%, is under some level of drought and half of Oahu was under severe drought as of November 30. An updated drought report is expected in the coming days.
CNN’s Travis Caldwell and Kelly McCleary contributed to this report.