Earlier on Sunday morning strengthening easterly winds had threatened to push the fire beyond containment lines.
Authorities now say the blaze is contained but not controlled.
The watch and act alert is in place for people bounded by Wattleup Road and the intersection of Rockingham Road and Cockburn Road to the south, the coast and Cockburn Road to the west, Gemma Road and Torgoyle Road to the north and Rockingham Road and Moylan Road to the east in parts of Henderson and Wattleup in the City of Kwinana.
Lives and homes remain under threat in the area and conditions could change.
The blaze started near the intersection of Rockingham Road and Lussky Road in Hope Valley on Saturday, prompting emergency warnings that forced people to flee.
People in the watch and act area on Sunday were told to leave if they planned to or had no bushfire plan.
Those who planned to stay and defend their homes were warned to make final preparations now. Mains water would be unreliable and homeowners should be patrolling their properties for spot fires.
Alert level warnings are in place for several areas around the watch and alert zone, with people in the alert areas to stay vigilant for signs of the fire.
While most of Western Australia has joined above average rainfall this year, the state's south-east, which includes Perth, has seen average to below average wet spells.
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