Blue skies presided over Presidents Day, a dramatic shift in weather from this weekend’s stormy, lightning- filled skies.

The islands were, for the most part, drying out Monday. But before planning outdoor weekend activities, Hawaii residents and visitors should brace themselves for another possible bout of wet, wintry weather.

“We could see some unsettled weather returning later this week,” National Weather Service lead forecaster Bob Burke said. “It could start as early as Thursday, but more likely Friday into the weekend. But it’s too early to tell.”

A winter weather advisory was in effect from Monday afternoon through 6 a.m. today for the Hawai island summits of Mauna Kea and Mauna Loa. The National Weather Service warned that accumulations of snow and ice are making for slippery road conditions and limited visibility.

Over the weekend, “an area of low pressure along with abundant moisture” lingered over the islands, causing thunderstorms to deluge many parts of Oahu.

The heavy rain flooded Kamehameha Highway, stranding motorists near Waikane. One Kaneohe man said a lightning strike created a giant hole in the roof of his townhouse, roughly 7 feet by 2 feet, allowing rain to pour through.

While parts of Windward Oahu were deluged over the weekend, with Waiahole receiving more than 14 inches of rain in a 24-hour period ending Sunday afternoon, two rainfall records elsewhere were shattered Sunday.

Honolulu received 0.83 inches of rain, breaking the old record of 0.56 inches set in 1995. And Kahului got 1.49 inches of precipitation, beating a 61-year record of 1.08 inches set in 1957.

Oahu was under a brown-water advisory Monday due to runoff caused by the heavy rainfall.

The public was specifically warned to stay out of waters near Kailua Beach Park and Kaneohe Bay due to a large sewage spill Sunday from nearby manholes.

An estimated 30,000 gallons of sewage was discharged into Kaelepulu Stream, which empties into Kailua Bay.

Another 10,000 gallons of effluent spilled into Kawa Stream from two manholes at the Kaneohe Pre-treatment Facility.

The state’s Clean Water Branch reminds people to stay out of the ocean because stormwater runoff may contain sewage, harmful microorganisms, and chemicals from commercial and industrial sources.

Another reason to stay out of brown water surfaced at Waimea Bay. Lifeguards spotted an 8-foot shark at 9:15 a.m. Monday about 50 yards from shore.

Officials said the shark displayed non-aggressive behavior. Sharks are attracted to possible dead animals in runoff.