A once-in-a-decade swell is set to hit the WA coast on Friday with waves between 40 and 50 foot expected in some areas.
The biggest waves are tipped for Margaret River, which should have big-wave surfers flocking to the region this weekend.
Bureau of Meteorology duty forecaster Paul Vivers said the swell has been on the rise throughout the week and should peak on Friday around five to six metres.
"This will also see bigger sets of up to twice that size [12 metres] in certain places and means we could see some 40-50 foot waves," he told Fairfax Media on Thursday.
Mr Vivers said these conditions were a very rare occurrence.
"This kind of swell, combined with light winds and huge wave periods, are seen once every 10 years."
A wave period - the time for two consecutive crests to pass a fixed point - is roughly 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 jet-skis out on the water towing surfers in" he said.
All coastal areas in the South West are expected to see significant swell before the size starts to weaken as it moves up the coast towards Jurien Bay and Carnarvon.
The cause of the huge waves is a deep low in the Indian Ocean which saw storm-force winds earlier in the week generate the swell which is headed towards the WA coast.
Mr Vivers 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 on Friday 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... make sure someone knows where you are," he said.
"If you will be on a jet-ski towing in [surfers] or observing the surf, 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.