"It's been better tonight than we had feared. The wind has been kind to us, so it has been spreading less quickly and at a much lower intensity. We have managed to limit the spread north-eastwards," Reidar Stokke from the South Trøndelag police told VG newspaper on Thursday morning.
Six fire helicopters, which have been grounded overnight, began work at the break of daylight on Thursday.
The fire on Frøya started at 11am on Wednesday morning, while another blaze was still burning in Flatanger, a municipality in neighbouring north Trøndelag county.
More than 300 people have been evacuated in case the flames spread to villages on the island, although according to the Adressa newspaper, so far only one building, a hiking lodge three kilometres west of the village of Sistranda has been caught up in the blaze.
The mayor of Flatanger announced at 1pm on Wednesday that the fire in his municipality had finally been extinguished, after it destroyed about 90 buildings in the coastal villages of Hasvåg and Småværet, and forced the evacuation of 33 residents from the area.
The absence of rain in northern Norway since December, combined with intense cold and high winds, has had the effect of freeze-drying heather and other vegetation, making it extremely vulnerable to fire.
On Wednesday, Norwegian authorities began warning people against lighting fires outside, or even leaving candles at the graves of relatives.