Perth is set to be blasted by freezing temperatures, heavy rainfall and gusty winds on the weekend as two strong cold fronts build momentum off the WA coast.

The first cold front is due to hit late on Thursday evening, and is expected to deliver massive amounts of rainfall through to Sunday morning.

Weatherzone senior meteorologist Jacob Cronje said Perth residents should batten down the hatches for heavy rain, gusty winds and a potential thunderstorm.

"The first pretty big cold front will be coming through late on Thursday and should be around until Sunday morning," he said.

"There will be a brief window of relief on Sunday afternoon, but on Monday morning a second cold front is expected to come through."

Perth got its first taste of what is to come on Wednesday morning, after nearly 10mm was dumped on the area over the course of 24 hours.

"Around five to 10 millimetres was recorded over a relatively short period of time this morning," Mr Cronje said.

"It's starting to clear, but should be completely done by Wednesday afternoon."

Wednesday morning's rainfall pushes Perth clear of the July monthly average, which currently sits at 220mm.

"We've already exceeded the July long term average by about 10mm, as we've recorded around 230mm to date," Mr Cronje said.

"And with these two cold fronts over the weekend, we're quite likely to exceed the average by quite a bit."

The south-west of WA is expected to cop the brunt of Thursday evening's cold front.

Main Roads WA issued a wet weather safety warning early on Wednesday morning, after poor visibility on Perth's major freeways brought traffic to a crawl at around 9am. 

Perth 7-day weather forecast

• Wednesday: 9 – 20, possible morning storm. Showers. Rain: 5 – 15mm.
• Thursday: 10 – 21, showers. Rain: 1 – 3mm.
• Friday: 14 – 19. Showers easing. Rain: 6 – 15mm.
• Saturday : 10 – 17. Possible shower. Rain: 0 – 2mm.
• Sunday: 10 – 18. Possible shower. Rain: 0 – 1mm.
• Monday: 11 – 17. Showers. Rain: 3 – 10mm.
• Tuesday: 7 – 17. Possible shower. Rain: 0 – 0.4mm.