A tropical storm watch was issued Saturday for the Hawaiian Islands as a weakened Tropical Storm Flossie churned eastward.
At 11 p.m. ET, Flossie was 770 miles east of Hilo, traveling west at 20 mph. It carried maximum sustained winds of 50 mph, down from 60 mph on Friday.
Tropical storm force winds of 39 mph or greater now extend 175 miles from the center.
Historically, tropical weather systems lose power as they hit colder waters on their way toward Hawaii, said Jennifer Robbins, a meteorologist for NBC station KHNL of Honolulu.
"It's all about the ocean temperatures," Robbins said. "There could be enough punch for it to cause a whole lot of rain."
Flossie was expected to be a minimal tropical storm when it arrives Monday but could still bring heavy rain through the islands.
The National Weather Service issued a flash flood watch from Monday morning through Tuesday night.
"Heavy rain associated with Tropical Storm Flossie will bring the threat of flash flooding across the main Hawaiian islands," the weather service said.