The National Weather Service said three tornadoes touched down in the Kunia area of Central Oahu Sunday.
Forecasters said they received reports of about a dozen funnel clouds in the area. Funnel clouds become tornadoes when they touch the ground.
Heavy showers were scattered across Oahu, particularly in the Central and Leeward areas. An Ewa Beach home had its roof blown off around 3:30 p.m.
Strong winds were reported on the Big Island, toppling trees and utility poles in various areas. About 33,000 customers across the island lost power during the day. There were no reports of injuries.
A flash-flood watch is in effect for all islands. Forecasters said that residents can expect more heavy rains starting Monday afternoon. There is a lower chance of funnel clouds, but there is a chance of seeing the twisters.