Maui officials say a wildfire in historic Lahaina town has burned parts of one of the most popular tourist areas in Hawaii.

Fire was widespread in Lahaina, including Front Street, an area of the historic town popular with tourists, County of Maui spokesperson Mahina Martin said in a phone interview early on Wednesday.

Traffic has been very heavy as people try to evacuate and officials asked people who weren't in an evacuation area to shelter in place to avoid adding to the traffic, she said.

Wildfires in Hawaii fanned by strong winds burned multiple structures, forcing evacuations and closing schools in several communities  and rescuers pulled a dozen people escaping smoke and flames from the ocean.

The US Coast Guard responded to areas where people went into the ocean to escape the fire and smoky conditions, Maui County said in a statement.

The Coast Guard tweeted that a crew rescued 12 people from the water off Lahaina.

A firefighter responding to the West Maui fire was taken to a hospital after experiencing smoke inhalation and was in a stable condition, according to Maui County.

Maui County tweeted that multiple roads in Lahaina were closed with a warning: "Do NOT go to Lahaina town."

The National Weather Service said Hurricane Dora, which was passing to the south of the island chain at a safe distance of 805 kilometres, was partly to blame for gusts above 97 kph that knocked out power as night fell, rattled homes and grounded firefighting helicopters.

Dangerous fire conditions created by strong winds and low humidity were expected to last through Wednesday afternoon, the weather service said.

'Every significant thing I owned burned'

Alan Dickar said he was not sure what remained of his Vintage European Posters gallery, which was a fixture on Front Street in Lahaina for 23 years.

Before evacuating with three friends and two cats, Mr Dickar recorded video of flames engulfing the main strip of shops and restaurants frequented by tourists.

"Every significant thing I owned burned down today," he said.

"I'll be OK. I got out safely."

Mr Dickar, who assumed the three homes he owns burned down, said it would take a heroic effort to rebuild what has burned in Lahaina, which is home to about 13,000 people.

"Everyone who comes to Maui, the one place that everybody goes is Front Street," he said.

Disaster declaration approved

Acting Governor Sylvia Luke issued an emergency proclamation on behalf of Governor Josh Green, who is travelling, and activated the Hawaii National Guard.

The Federal Emergency Management Agency approved a disaster declaration to provide assistance with a fire that threatened about 200 homes in and around Kohala Ranch, a rural community with a population of more than 500 on the Big Island, according to the Hawaii Emergency Management Agency.

When the request was made, the fire had burned more than 243 hectares and was uncontained.

Much of Hawaii was under a red flag warning that continued Wednesday, and two other uncontrolled fires were burning on the Big Island and Maui.

Fire crews on Maui were battling multiple blazes concentrated in two areas: the popular tourist destination of West Maui and an inland, mountainous region.

It wasn't immediately known how many buildings had burned or the number of people evacuated, County of Maui spokesperson Mahina Martin said in a phone interview late on Tuesday.

However, she said there were four shelters open and that more than 1,000 people were at the largest.

"This is so unprecedented," she said, noting that multiple districts were affected.

An emergency in the night is terrifying, she said, and the darkness makes it hard to gauge the extent of the damage.

Because of the wind gusts, helicopters weren't able to dump water on the fires from the sky — or gauge more precise fire sizes — and firefighters were encountering roads blocked by downed trees and power lines as they worked the inland fires, Ms Martin said.

About 14,500 customers in Maui were without power early Wednesday, according to poweroutage.us.

"It's definitely one of the more challenging days for our island given that it's multiple fires, multiple evacuations in the different district areas," Ms Martin said.

Winds were recorded at 129 kph in inland Maui and one fire that was believed to be contained earlier Tuesday flared up hours later with the big winds, she added.

"The fire can be a mile or more from your house, but in a minute or two, it can be at your house," Fire Assistant Chief Jeff Giesea said.

In the Kula area of Maui, at least two homes were destroyed in a fire that engulfed about 4.5 square kilometres, Maui Mayor Richard Bissen said.

About 80 people were evacuated from 40 homes, he said.

"We're trying to protect homes in the community," Big Island Mayor Mitch Roth said of evacuating about 400 homes in four communities in the northern part of the island. As of Tuesday, the roof of one house caught on fire, he said.

Fires in Hawaii are unlike many of those burning in the US West.