As the east coast enters a heatwave that could trigger rolling black outs, Perth has recorded its coldest February day on record and its second biggest downpour.

There has been traffic chaos across the city as major roads flood.

The mercury reached just 17.4 degrees on Thursday making it the coldest February day since records began more than 100 years ago.

Perth is on track for its wettest day on record. Rick Stevens KRS

While the weather if forecast to be warmer on Friday, with the temperature expected to reach 27 degrees, the rain continues to drench the city.

An overnight deluge pushed total rain recorded since 9am Thursday to more than 110 millimetres. It is the city's wettest day in 25 years and the second wettest day on record after a 120.6 millimetres fell on February 9, 1992.