A large forest fire north of Napier has now spread to over 300 hectares, with crews heading out for a second day to tackle it.

Trevor Mitchell, the principal rural fire officer for Hawke's Bay, said the overnight doubling of the fire was unexpected, but it is "still within containment area".

It was spreading northeast from Tangoio Settlement Rd and Mitchell said it was unlikely to be put out today.

Helicopters with monsoon buckets and at least 65 firefighters were battling eight fires around the Hawke's Bay region on Monday, including one in Waipatiki Forest that was burning out of control.

Mitchell said that fire hadn't crossed any roads overnight, with State Highway 2 still "miles away" from the flames.

He advised people to keep off Tangoio Settlement Rd, "unless you absolutely need to do business at Waipatiki".

He said the fire would likely be an issue for a few days until they got a perimeter around it.

Most firefighters withdrew from the fire on Monday by 6.30pm due to windy and dangerous conditions.

By 9.30pm the fire had spread to 140ha and one house had been evacuated as a precaution.

Mitchell said the terrain and conditions meant that the forest fire would be left to burn overnight.

Firefighters and aircraft could not fight the fire in darkness, he said.

Winds have eased this morning but while isolated showers are forecast today there will not be any steady rain.

A separate grass fire that broke out in Fernhill, Hawke's Bay on Monday was extinguished. Police asked motorists to avoid State Highway 50 as choking smoke covered the road.