Guam is in a recovery phase after being pummelled by typhoon Mawar. In a notice yesterday morning, Guam Waterworks Authority asked customers to conserve water while its services get restored.

A precautionary boil water notice was also in place until laboratory analysis confirms water is safe to drink.

The islands' power authority said it had begun its post-typhoon restoration process following widespread outages.

It said crews were working around the clock to clear lines and restore electricity.

"We are working to restore your power service as soon as possible," it said.

"We ask residents not to inundate or overwhelm Guam Power Authority Trouble Dispatch lines with inquiries regarding service restoration."

On Thursday evening (local time), Governor Lou Leon Guerrero removed the typhoon warning for Guam after consulting with the National Weather Service.

"We have weathered the worst magnitude of typhoon," Guerrero said in a video.

"I am now declaring Guam condition of readiness four effective 5pm."

A spokesperson from United States Indo-Pacific Command said it was ready to provide support to "whatever assistance is deemed necessary" by the Federal Emergency Management Agency (FEMA) and local government officials.

The spokesperson said they had deployed initial assessment teams to survey the damage.

The worst of typhoon Mawar was experienced on Wednesday night in Guam with sustained winds of up to 225 kilometres per hour and in some locations with rain exceeding 50 centimetres in the space of 12 hours.

Cars were flipped and corrugated iron was torn off roofs.

The eye of the storm went through the Rota channel and briefly clipped northern Guam. Damaging winds continued into Thursday.

Meteorologist Landon Aydlett, from the US National Weather Service office in Guam, said it would take weeks for the island to clean up the mess.

"We are waking up to a rather disturbing scene out there across Guam," Aydlett said.

"We're looking out our door and what used to be a jungle looks like toothpicks, it looks like a scene from the movie Twister, with trees just thrashed apart, we lost most of our non-coconut trees out their yesterday evening. We have a mess on hand."

A spokesperson from FEMA told RNZ Pacific two people were injured in Guam and there were no fatalities.

The Public Information Officer for the Governor of Northern Mariana Islands, Frankie Eliptico, said Rota took the biggest beating out of all the CNMI islands.

Eliptico said there had been no reports of major injuries or fatalities in the Marianas.

"No major damage has been reported from this morning but again those assessments are still being conducted," he said yesterday.

"There have been some communication towers that have been affected but as far as major damage that we are seeing on Guam we are not seeing here in the CMNI."

RNZ Pacific's CNMI correspondent Mark Rabago said government agencies were closed on Thursday and schools would remain shut on Friday (yesterday).

Rabago said the priority for Rota was now to prepare ports to collect supplies.

"Their first mission once the sun comes out is go to the docks, that means to go to the airports, go to the seaports and clear the access roads going through it, so when supplies do come in they won't have any difficulty bringing those supplies who really need it."

In a statement FEMA said over 130 staff are ready to help local response efforts in Guam and the Northern Mariana Islands. Over 100 generators as well as emergency communication equipment were also being sent.

Mawar was upgraded to a super typhoon after passing the Mariana Islands and could threaten Taiwan or the Philippines early next week.