A "once in 10 year swell" is set to hit the WA coast tomorrow with waves of between 40 and 50 foot expected in some areas.
The biggest waves are expected to be seen around the Margaret River area which means big-wave surfers are likely to flock to the region over the weekend.
Duty forecaster from the Bureau of Meteorology Paul Viviers said the swell has been on the rise throughout the week and is expected to peak tomorrow at around five to six metres.
"This will also see bigger sets up of to twice that size (12 metres) in certain place and means we could see some 40-50 foot waves," he told Fairfax Media on Thursday.
Mr Viviers said these conditions were a very rare occurrence.
"This kind of swell combined with light winds and huge wave periods are seen once very 10 years."
He said usually a wave period, the time for two consecutive crests to pass a fixed point, was around 14 seconds but this swell could see periods of between 18 and 20 seconds.
"This will make for some really big sets. The kind where I'd expect to see jetskis out on the water towing surfers in" he said.
All coastal areas in the South West are expected to see significant swell, with the size weakening as it moves up the coast towards Jurien Bay and Carnarvon. There is also significant swell expected for Saturday although it will start decreasing in size from tomorrow evening.
The cause of the huge waves is a deep low in the Indian Ocean which saw storm-force winds of up to 200km/h earlier in the week generate the massive swell which is now headed towards the WA coast.
Mr Viviers said while conditions would be perfect for big-wave surfing they would be less than ideal for the general public and fisherman.
Margaret River Sea Rescue volunteer Jock Salkeld warned anyone planning to do any fishing or surfing in the area to be very aware of the conditions tomorrow and at the weekend.
"If you're going to go out then make sure you're in peak physical condition and don't take any risks," he said.
"Make sure someone knows where you are as well
"If you will be on a jet-ski in the area towing in [surfers] or observing the surf then make sure it's serviced and in good condition and you have all the required safety gear."
Mr Salkeld also had a warning for anyone planning to do any sightseeing tomorrow to watch the hit the beach or the rocks.
"Observe the conditions for at least half an hour beforehand because there will be freak waves tomorrow a lot higher than your average swell," he said.