Update 8:17 p.m.
The National Weather Service issued a flash flood warning for Oahu after radar showed heavy rain over ht Koolau mountains, falling at a rate of 1 to 2 inches an hour just after 8 p.m.
The Waiahole Stream has risen just above flood stage, which, in the past, has led to flooding on Kamehameha Highway at Waiahole Valley Road.
The warning includes Maunawili, Kailua, Waikane, Hauula, Kaneohe, Waiahole, Kahaluu, Marine Base Hawaii in Kaneohe, Ahuimanu, Kahuku, Punaluu and Kaaawa.
The advisory is in effect until 11:15 p.m.
Update 7 p.m.
A flood advisory for Hawaii island has expired tonight as heavy rains south of Hilo eased, the National Weather Service reported.
Forecasters say there’s still a chance of heavy showers over Hawaii island through Tuesday because of instability in the atmosphere and the amount of tropical moisture in the air.
Update 4:20 p.m.
The National Weather Service issued a flood advisory for Hawaii island after radar indicated heavy rain south of Hilo falling at a rate of 1 to 2 inches an hour at about 3:24 p.m.
The advisory includes Hilo, Hawaiian Paradise Park, Mountain View, Keaau, Volcano, Glen wood, Orchidlands Estates, Hawaiian Acres, Hawaii Volcanoes National Park, Ainaloa, Kurtistown and Fern Acres.
It is in effect until 6:30 p.m.
Instability in the atmosphere and heavy humidity is expected to produce heavy showers over the Big Island through Tuesday, with a slight chance of thunderstorms, forecasters said.
Not only will the weather be muggy with the chance of rain, but forecasters say vog could move over Oahu as a weather system disrupts the tradewinds for the next few days.
Light and variable winds are bringing tropical moisture over the islands from the south, bringing uncomfortable humidity.
Forecasters expect the hot and humid weather to cause clouds to build up over leeward and interior sections that could bring afternoon showers.
“Showers will become more frequent, especially during the afternoons and early evenings, as a moist and somewhat unstable airmass moves across the area. Locally heavy rainfall and isolated thunderstorms will be possible on the Big Island through Tuesday,” forecasters said.
Southeasterly winds are also expected to bring vog over Oahu and other islands by Tuesday.
The muggy conditions are expected to remain over the islands through Wednesday.
Forecasters expect the cooling tradewinds to return on Thursday.
The forecast for Honolulu and south shores of Oahu calls for highs between 84 and 90 degrees with a 50 percent chance of showers during the day through Wednesday and a 40 to 50 percent chance of rain Thursday.