The alert for Lancelin was originally an emergency warning but downgraded to a watch-and-act shortly before midnight as the fire was contained but it is not yet under control.
"There is a possible threat to lives and homes as a fire is burning in the area and the conditions are changing," WA's Department of Fire and Emergency Services (DFES) said in a statement, noting that Lancelin Road, north of Perth, was closed.
Authorities said in their latest update an evacuation centre at Guilderton Country Club was being closed.
The fire was burning northwest towards the townsite, 126km north of Perth.
Locals have been told to close all windows and doors as they leave, turn off evaporative air conditioners and try and keep water running as they leave.
Those who can't leave have been told to shelter in their homes in the room furthest from the fire front in a room with two exits and water, such as a kitchen or laundry.
Lancelin is one of several towns issued with bushfire warnings on Wednesday.
DFES issued warnings that lives and properties are under threat across the Wheatbelt in parts of Toodyay, Coondle and Julimar, about 100km northeast of Perth.
"It's too late to leave, leaving now will put your life in danger," the department said.
The emergency warning covered people in an area bounded by Trig Road, Coondle West Road, Parkland Drive including Sinclair Place and Donegan  View, Julimar Road and across to Nerramine Drive.
People north of Julimar Road can leave in an easterly or westerly direction.
An evacuation centre has been set up at Toodyay Memorial Hall.
Homes on Parkland Drive, Munnapin Rise, Malkup Brook Road, Sand Spring Road, Howard Road, Powder Bark Road, Sinclair Place and Donegan View are threatened by fire.
A number of roads have been closed, including Julimar Road from Chittering Road to Coondle West Road.
The Shire of Toodyay borders the northeastern edge of the Perth metropolitan area and has a population of about 4600 people.
Another emergency warning was issued in the shire of Manjimup - in the state's southwest - for Callcup, Crowea and Meerup after a fire broke containment lines on Thursday morning.
"You are in danger and need to act immediately to survive. There is a threat to lives and homes," DFES said.
The alert was in place for the area bounded by Gumnut Road and Richardson Road, Tattenham Road and Pemberton-Northcliffe Road as well as Malimup track and Barker Road.
The Bureau of Meteorology warned fresh easterly winds and dry conditions would lead to elevated fire dangers.
"There is also the risk of high-based thunderstorms with dry lightning, exacerbating the fire dangers," the alert said.
Total fire bans have been enacted for the Perth Metropolitan, Goldfields Midlands, South West districts on Thursday.
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