A woman lost on a Waikato mountain was rescued after contacting her family by Facebook on her phone - but could have been found sooner if she had simply called police.

Family of the 41-year-old contacted police after receiving a Facebook message from her at about 2.30pm yesterday saying she was lost on Mt Te Aroha.

Police launched a search and rescue operation shortly after that.

Sergeant Dave Raffan said the woman had left her car at the Wairongomai car park and climbed up towards Mt Te Aroha, leaving the main track.

"She was wearing only light clothing and jeans and weather at the time was wet with low cloud," he said.

Once the alarm was raised police were able to narrow down a search area by 7pm, thanks to new phone tracking technology.

"SAR teams then moved into the area and located her in a stream about 200m from the car park about 8.20pm," said Mr Raffan.

"Wet, cold and tired the woman was walked out and reunited with her family who expressed their sincere thanks to all those involved."

He said while everyone involved was "very happy" that the woman had been found safely, there were several factors that could have concluded the search sooner.

"If going for a day for instance, ensure you're equipped to spend the night if you have to," said Mr Raffan.

"Secondly, if going into the bush tramping, don't leave the tracks and tell friends and family which tracks you intend using. That way, if something goes wrong we know where to start looking for you.

"Thirdly, ensure that the emergency services are the first people you contact to raise the alarm, you never know, your battery could give out and that first call maybe the only one you get to make."