The Chatham Islands has felt the brunt of ex-tropical Cyclone Pam overnight and more damaging winds and sea surges are expected throughout the day.

In its latest update, MetService said Cyclone Pam was located about 420km southeast of the Chatham Islands. It said the system remained a "very intense mid latitude cyclone" that was moving southeast away from the Chatham Islands at about 20km/h.

MetService said "damaging gales" of up to 120km/h which have been battering the area were expected to last through to tonight.

Heavy swells of up to nine metres would also continue to surge this morning, before easing tomorrow.

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Another 20 to 30mm of light to moderate rain was also expected to fall through to midnight tonight, MetService said.

Speaking to Radio New Zealand this morning, Rebecca Coleman from the Chatham Islands Police said the winds had picked up again this morning.

"We're expecting to hear from residents this morning after they have had a chance to have look around as to how things have gone, but so far looking reasonably good."

There had been no reports of any damage to any homes over night, Ms Coleman told RNZ.

"We haven't had any calls over night in our emergency centre, people have stayed inside.

"I am aware that out towards Owenga it was quite rough last night and there were a few reports online that we could see that some tunnel houses... have started to come apart.

"As I said we will expect that we can start seeing what else has been going on quite shortly as people can have a chance to look around."

Ms Coleman said there were "a few" houses around Waitangi that remained without power this morning.

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"My understanding is that could be for a couple of days," she said.

Chatham Islands mayor Alfred Preece said some homes remained without power this morning, and 12 people were bunkering down in an evacuation centre.

"A lot of other families have moved in with other family members."

There had been no reports of any major damage to any homes, Mr Preece said.

"We've had a blustery old night, but it has sort of calmed down briefly, about 3am, and has ramped up again this morning."

Mr Preece said there was some damage, but he was reluctant to elaborate until the storm had subsided.

"We've got power lines down, we've got trees down... we're not too concerned about little bits and pieces until it has passed."

Power would hopefully be restored to those homes without today, depending on whether strong winds died out, Mr Preece said.

"It would be extremely dangerous where the power lines have come down. We don't want to put our staff in danger."

Schools and businesses would remain closed this morning, and a call would be made later today as to whether they would re-open tomorrow.

"We've had damage, things have closed down. We'll review things today and if the wind dies down things will crank back up slowly and we will be able to review what damage has occurred and go from there," Mr Preece said