Fire crews were called to the blaze shortly after 2pm today, on Whangārei Heads Road between Onerahi and Tamaterau.
Ten trucks and four helicopters were in attendance.
Fire and Emergency's Northland District manager Wipari Henwood said a number of houses were being evacuated, and crews were undertaking a reconnaissance flight to confirm how many structures were at risk.
He said the fire was burning in a "problematic area", with numerous access points.
Northland Fire and Emergency said if you have not been told to evacuate, but feel unsafe, please self-evacuate if you are able to.
It was advised people affected by the smoke to close windows and doors and reduce outdoor exercise. Air conditioning should be switched to 'recirculate' or turned off and pets should be kept inside with clean food and water.
A large amount of smoke could be seen at Whangārei Heads.
A resident, who lived about a kilometre from the fire, said it was scary and bigger than she had seen in previous years.
She said she could see flames and several helicopters pouring buckets of water on to the fire.
Ryan Houbar lives near Whangārei's port and said the smoke from the fire had been drifting over from across the harbour and was visible from where he was at Port Nikau.
"There's this big plume of smoke coming off it and it's coming down through where we are down at the port and it looks like quite a large fire. We can definitely smell it all down here and it's getting pretty hazy down here."
The weather has been mostly dry for a couple of weeks, with all but a few instances of light showers, he said.
Paul Doherty, a church deacon in Onerahi, said he was one of about a dozen people at a lookout at the end of the Whangārei Airport runway.
From there they could look directly across the water to the fire at Waikaraka.
He could see several helicopters at work, scooping water from the harbour and dumping it on the fire.
"There's smoke billowing all across the airport, and down the other side of the harbour towards Oakleigh. It seems to be less intense than it was, which is a good sign."
Through the haze he could see a number of homes on the hillside but they did not appear to be in immediate danger.
Weather outlook
Dry, breezy weather in Northland is largely set to continue over the next 24 hours.
Metservice meteorologist Mmathapelo Makgabutlane said the wind around Whangārei Heads will ease this afternoon, but pick up again on Friday.
While there was a chance of a shower on Friday, she said it likely won't be enough to put a fire out.
Whangārei Airport remains open and airport duty manager Gareth Worswick said the fire was close, but an easterly wind was blowing the smoke away from the runway so visibility remained good.
Road reopens
The Whangārei District Council said Whangārei Heads Road had reopened but with a 30kmh speed limit near the Beach Road intersection at Onerahi.
Motorists were advised to drive with caution, be prepared for smoke, and give way to emergency vehicles.
People wanting to take another route to Whangārei Heads can use Mount Tiger Road.
Whangārei Heads Road was closed earlier this afternoon at Waikaraka, between Onerahi and Tamaterau.
