Weather: 'Extreme seas', raging swells unleashed against Auckland

"Extreme seas" and raging swells are being unleashed against Auckland's west coast as rough weather whips up wild waves.

Video taken by NIWA on Saturday morning shows Muriwai being slammed by a dangerous combination of a cold front and king tides.

"Big waves will impact the west coast of both islands over the next 36 hours. And with king tides this weekend, there's a risk for 'overtopping' in localised areas," NIWA warned on Twitter.

These waves could top 10 metres, and lead to an increased risk for the public.

"Auckland: The combination of king tides and large combined waves (extreme seas + heavy swells) are likely to produce unusual wave 'run-up' onto the western beaches this weekend," MetService warns. "Take care, as this type of rogue wave can catch you out."

Surf Life Saving warns people not to swim, surf or fish alone due to the conditions - and says if people get into trouble there will be no lifeguards to save them.

"Lifeguards are currently not on duty, and there is a heightened risk for those people that may get in trouble in the water due to extended response times for tasking lifeguards in the winter months," Surf Life Saving Northern Region said on Facebook.

"We ask that members of the coastline avoid recreating in and around the water for the small period that the increased swell and tides are in effect and to be cautious and use common sense.

"As lifeguards are not on duty Surf Life Saving recommends that if you see someone in trouble, you immediately dial 111 and ask for the police."

The rest of the day for the upper-half of the North Island isn't expected to be much better, with blustery winds gusting to around 70km/h. The air is straight from Antarctica - 72 degrees south of the equator. 

"This is the coldest we have had this winter," meteorologist Stephen Glassey told Stuff. "We haven't seen any snow to anywhere near sea level yet and this will be the first time it gets close to that."

NIWA warns this could lead to isolated wind damage and the risk of high-sided vehicles getting bumped around.

Newshub.