More snow could fall and heavy rains are possible on the Big Island through mid-week.

The summits of Mauna Kea and Mauna Loa are under a winter weather advisory until 6 p.m., where snow, ice and freezing fog could make travel to the summit hazardous.

Up to an inch could fall Monday and more isolated snow and rain showers are possible through Thursday night.

Warm moist air from the south and colder air above it are creating the unstable conditions.

Most of the rain threat is on the Big Island and Maui. Thunderstorms are possible on Hawaii Island.

Oahu and Kauai may also see some showers, especially in windward and mauka area, but skies should remain mostly sunny, forecasters said.

Forecasters expect the threat of rain to lessen by the end of the week.

Tradewinds will be breezy at 15 to 20 mph through the end of the week.

A high surf advisory is in effect for north and west shores of Kauai County, Oahu and Molokai and for north shores of Maui until midnight.

Forecasters expect a north-northwest swell to build Monday morning and steadily decline Monday afternoon and evening.

Waves could reach 15 to 20 feet Monday, declining to 10 to 15 feet in the afternoon on north shores. Waves of 8 to 12 feet are expected on west shores.

The forecast for Honolulu and south shores of Oahu calls for breezy tradewinds, a 50 percent chance of scattered showers Monday night through Friday, with highs between 77 and 82 degrees and lows between 65 and 71 degrees.