Umbrellas mushroomed all around O'ahu yesterday, including this cluster near the state Capitol. A flash-flood watch issued yesterday by the National Weather Service will remain in effect through this afternoon for all islands but the Big Island. Photos by Gregory Yamamoto • The Honolulu Advertiser

The view from the Pali Lookout, with Kane'ohe under showers in the late afternoon yesterday.

Blue skies can lead to heating and that in turn can lead to thunderstorms this afternoon and tonight, said Maureen Ballard, a meteorologist for the weather service.

Rain will likely not be as widespread or fall as heavily as it has for two nights, she said.

"It will be hit or miss but it could start some problems," Ballard said. "That's why we continued a flash flood watch for Kaua'i and O'ahu."

The flash flood watch, which was extended through this afternoon, also includes the rest of the state, Ballard said.

Drier conditions are expected, along with increasing tradewinds, by late tomorrow, according to the weather service forecast.

The upper-level low pressure system — which created warm, unstable atmospheric conditions over the state — had drifted south to the Big Island early this morning, and heavy rainfall cells had drenched the Ka'u district with 1 to 1.75 inches of rain per hour, Ballard said.

Last night, the Big Island community of Pahala received the most rain with 1.02 inches falling between 11 p.m. and 5 a.m.