Olaf intensified into a major Category 4 hurricane Monday and continued to gather strength as it headed into the Central Pacific overnight.

The storm remains far from the Hawaiian Islands and should weaken if it takes a turn into cooler waters, as forecasters predict.

At 5 p.m. Monday the storm was 1,235 miles east-southeast of Hilo, moving west at 10 mph with maximum sustained winds of 140 mph.

Hurricane-force winds extended 30 miles from the center; tropical storm-force winds extended 140 miles from the center.

On its current forecast path, Olaf is expected to turn toward the west-northwest today and toward the northwest Wednesday. If so, Hawaii would likely be spared from the storm’s destructive winds and rain.

Forecasters warn that the track could change.

Even if the storm stays on course, Hawaii could still see high surf and a possible change in wind direction.

High surf generated by Olaf is expected to begin arriving at the Big Island by Wednesday and other islands by Thursday. Wave heights could reach warning levels on eastern shores of the Big Island.

Surf on other islands will depend on Olaf’s track and how strong the storm gets.

The storm has rapidly gained strength since becoming a Category 1 hurricane Sunday.

Under the Saffir-Simpson wind scale, a Category 1 hurricane has maximum sustained winds between 74 and 95 mph. A Category 4 hurricane has maximum sustained winds in the range of 130 to 156 mph.

Olaf is the 11th hurricane of the Eastern Pacific season and the 15th tropical cyclone in the Central Pacific.

Meanwhile the high temperature of 91 degrees in Honolulu on Monday tied the record for the date, set in 1996, the National Weather Service said.

The National Weather Service predicts a slight increase in tradewinds today and Wednesday due to a high-pressure system passing to the north.

Winds are expected to diminish later in the week as the system moves off to the northwest.

Satellite imagery shows an area of clouds and showers embedded in the trades moving eastward toward the state, which could result in increased showers over the Big Island spreading up the island chain through this afternoon. Showers will be focused over windward and mauka areas.