Hurricane Nolo strengthens as it passes Hawaii, bringing heavy rain. See its path.

Hurricane Nolo was on the verge of becoming a major Category 5 storm early Monday as it moved farther away from Hawaii, the National Hurricane Center said. It was expected to continue gaining strength, reaching peak intensity on Monday before gradually weakening.

The storm is forecast to remain well south and southwest of Hawaii's main islands but approach the Papahanaumokuakea Marine National Monument on Tuesday. That's a vast, 582,000-square-mile protected conservation area northwest of Hawaii. 

Map shows Hurricane Nolo's expected path

Nolo had maximum sustained winds of 155 mph early Monday, making it a Category 4 storm. Hurricane-force winds were extending outward up to 35 miles from Nolo's core and tropical storm-force winds extended outward up to 150 miles.

Nolo was forecast to bring up to 20 inches of rain to the eastern and southern portions of the Big Island. For Maui, 4 to 8 inches were possible. The rest of Hawaii was likely to get 1 to 3 inches, with 5 at most, enough to trigger isolated flooding, forecasters said.

What's more, Nola-generated swells "will be affecting south-facing shores of the main Hawaiian Islands for the next few days. These swells are likely to cause life-threatening surf and rip current conditions," the hurricane center cautioned early Monday. 

All state parks on Hawaii's Big Island and on Maui were closed because of the storm, the state's Department of Land and Natural Resources said. 

President Trump on Friday approved an emergency declaration for Hawaii that will provide federal resources and assistance to the state in its recovery from Nolo, Hawaii Gov. Josh Green said.    

Nolo formed as another storm, Hurricane Polo, continued to swirl in the Pacific, off Mexico's southwestern coast.

The latest storms add to an unusually active season in the Pacific. Earlier this month, Hurricane Lowell brought damaging winds and heavy rain to the western Hawaiian islands of Kauai and Niihau, bringing down trees, damaging roads and knocking out power for thousands.

Last month, Hurricane Lala washed away about 100 homes, triggered landslides and caused widespread power outages as it brushed past Hawaii.