National Weather Service meteorologist Vanessa Almanza said: “It’s definitely going to be a triple threat.” Precipitation from the storm is expected to range from five to 15 inches.
Ms Almanza added it is “probably not a good day to go to the beach.”
The storm weakened on Saturday as it came closer to Hawaii, but officials have warned residents against feeling too confident.
Robert Ballard, the science and operations officer at the Central Pacific Hurricane Center, said: “Douglas is continuing a gradual, slow, weakening trend, which in itself is good news, but the bad news is that this hurricane is going to come very close to the islands even as it’s weakening.
“And we do expect significant impacts as it makes its point of closest approach or possible landfall as it comes through.”
Authorities on Oahu and Maui raised the alarm as downpours and gusty winds shook trees.
They advised locals to shelter where they are or, if necessary, to retreat to shelters.
A hurricane warning was in place for Oahu, Kauai and Maui, however, a hurricane watch was called off for the state.
On Sunday, the hurricane was expected to bring along sustained winds of 140 kph (85 mph).
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State health department officials spoke to the 625 residents who were currently in isolation or quarantine as of Friday due to a coronavirus diagnosis or because they have been in contact with someone who tested positive for the virus.
Each one of those people confirmed that they would shelter-in-place and not seek help at a hurricane shelter.
Honolulu Mayor Kirk Caldwell said: “That gives a sigh of relief.”
Hawaii is one of the states in the US with the lowest COVID-19 infection rates, although those numbers have been on the rise in recent weeks.
Every day since Thursday, Hawaii has announced record numbers of daily infections, including 73 new cases on Saturday.