While Kilo remained a distant threat to the state Sunday, heavy rain and thunderstorms caused by an unstable air mass hammered parts of Oahu and Kauai.

At 5 p.m. Sunday, Kilo was about 715 miles southwest of Honolulu and about 270 miles east-southeast of Johnston Atoll, where a tropical storm watch was posted.

The storm recorded maximum sustained winds of 35 mph and was moving west-northwest at 8 mph. It was expected to strengthen into a tropical storm late Sunday or early Monday and gradually intensify into a hurricane.

The storm is expected to begin a turn to the north by Monday, but it shouldn’t make a sharp turn to the northeast, back toward the main islands. Kilo’s latest forecast path takes it near Johnston Atoll and into t he Papahanaumokuakea National Marine Monument and keeps it away from the main Hawaiian Islands.

However, forecasters caution that Hawaii residents should keep monitoring the storm because the margin of error is large on forecasts five days out, and the path is likely to change.

Of more immediate concern Sunday was the moist air mass drawn over the islands by a southerly flow to the east of Kilo. According to the National Weather Service, a weak trough to the north has kept the system unstable, resulting in stormy conditions across the island chain.

Oahu and Hawaii island spent much of the day under a flash flood warning, while Kauai and Maui were under a flash flood advisory.

Radar showed heavy showers and thunderstorms affecting north and northwestern parts of Kauai at 1:48 p.m. A flood advisory was issued for Kokee to Na Pali to Princeville until 5 p.m.

The heavy showers prompted the Department of Land and Natural Resources to close the Kalalau Trail until further notice. Kauai Civil Defense officials also canceled siren testing scheduled for Monday through Friday to avoid confusion during Kilo’s possible approach.

Heavy rain over Windward Oahu between Saturday night and Sunday morning prompted a brown-water advisory for windward waters from Waikane to Kailua Beach.

The advisory warned the public to stay out of floodwaters and storm water runoff due to possible overflow from cesspools, sewers and manholes, as well as pesticides, animal fecal matter, dead animals, pathogens, chemicals and associated flood debris.

At 3:36 p.m., radar images showed nearly stationary torrential rain and thunderstorms over central and northern Oahu, the National Weather Service reported.

In a three-hour period ending at 5 p.m. Sunday, gauges in Mililani recorded 2.32 inches of rain. Wheeler Army Airfield recorded 1.93 inches over the same period.

The deep tropical moisture is expected to linger over the island through the early part of the week, resulting in continued locally heavy showers and thunderstorms.

A flash flood watch remains in effect for all islands through 6 p.m. Monday.

Kilo was also bringing a small southwest swell to south and west shores. Wave heights of 3 to 5 feet are expected through Monday on south shores, and 2- to 4-foot faces are expected on west shores.

Meanwhile the heat tied the record in Hilo on Sunday. The high temperature of 88 degrees tied the record set in 2007.