An anxious wait for residents on Kaipara's Pouto Peninsula.

The settlement of Kellys Bay is in the line of a fire which has been burning through forest since Monday night.

Around 150 firefighters are battling the blaze, with a crucial afternoon ahead - winds are forecast to change direction, and get stronger.

Residents have been told at a meeting this morning to be prepared to evacuate.

The Department of Conservation's Sue Reed-Thomas says it's being fuelled by plenty of undergrowth and thinning, so the focus is on containment.

"We've got ground crews operating in key places as well as helicopters and machinery to create fire breaks, and try and just prepare ourselves for the worst to day if that wind picks up."

There are around 40 properties in the beach-side settlement, with five thought to be at risk.

Nearby Pouto School has closed for the day.