Motorists are being urged to drive carefully with a significant amount of fog in the southern suburbs.
Main Roads has advised there is reduced visibility on the Kwinana Freeway between Mundijong Road and Rowley Road.
Mandurah Road between Dixon Road and Rockingham Road has also been affected.
Drivers should switch headlights on, ensure a safe braking distance and allow for extra travel time.
A smoke alert is also current for Perth's northern and eastern suburbs, including the Perth CBD, in the Perth metropolitan area.
The smoke is the result of prescribed burns being carried out in Julimar State Forest and east of Dwellingup, as well as private property burning.
It is expected to clear by mid morning.
UPDATE: FOG OVER ROAD - AFFECTING SOUTHERN SUBURBS
— Main Roads WA (@Perth_Traffic) May 12, 2019
Kwinana Freeway between Mundijong Road and Rowley Road
Mandurah Road between Dixon Road and Rockingham Road
REDUCED VISIBILITY IN THE AREA https://t.co/tZFEdtcok9 #perthtraffic
Digital drivers' licences to be introduced in WA
Mandurah FIFO worker wins $250k
2026 ANZAC Day services across the Peel and Rockingham regions
Mother of 11-year-old boy killed in Mandurah scooter crash found safe and well
Peel charity desperately seeks funds to keep doors open
Australind train service set to resume
Thunder premiership player Traye Bennell hangs up the boots
Works underway to protect 200-year-old 'Big Tree' in Greenfields
Wanted man believed to be in Mandurah area