The ACT will face three consecutive days of total fire bans for the first time since the 2003 Canberra bushfires.
The total fire ban will be in place from the beginning of Thursday through until the end of Saturday.
The ACT has already had more total fire ban days this fire season compared to the entirety of last year's season.
Acting chief officer of the ACT Rural Fire Service Rohan Scott said the number of fire bans this early in the season was "uncommon".
"We have got a very dry landscape at the moment, and this is a preventative measure to stop any ignition," Mr Scott said.
"For the next three days it's going to be very dry out there and we're looking at unpredictable fire behaviour.
"I wouldn't say it's exactly the same conditions as conditions in 2003, but it is very dry across the ACT and NSW."
The total fire bans come as Canberra prepares to swelter through extreme conditions with temperatures expected to climb to 40 degrees on Thursday.
The Bureau of Meteorology has predicted the mercury could reach 42 degrees on Saturday, which would set a new temperature record in the capital for December.
The hottest December temperature previously recorded in the ACT was 39.2 degrees in 1994.
The hottest temperature on record was 42.2 degrees, set in February 1968.
Extra ambulance crews are being put on over coming days to help deal with the extreme temperatures.
Smoke from bushfires to the east of Canberra near Braidwood and on the South Coast is also exacerbating conditions in the capital.
The ACT government's air quality monitoring stations have recorded conditions as hazardous in all locations.
It's expected the smoke haze, which has been hanging over Canberra for several weeks, will continue until at least Saturday, fuelled by strong easterly winds.
The total fire ban has forced the closure of all of Namadgi National Park during the three-day period.
Campgrounds in the area will also be closed off to visitors as a safety measure.
Executive general manager of the Environment, Planning and Sustainable Development Directorate, Ian Walker, said further preventative steps have been taken to ensure bushfires don't begin in national parks across the ACT.
"There will also be a prohibition on open flames or fires in ACT national parks until the end of the fire season," Mr Walker said,
"It's a strategy to reduce risk from campfires escaping or visitors inadvertently causing a spark."
Fire towers within the national parks will be staffed from Wednesday.
"We have rangers out there monitoring the conditions, and part of their role is the make sure visitors are not placing themselves at risk."
As Canberra braces for heatwave conditions, paramedics have urged for residents to stay indoors and avoid the heat.
ACT Ambulance Service general manager Matt Smith warned Canberrans who can't avoid being outdoors due to work limit their exposure.
"We want to remind the community not to be complacent when it comes to hear because extreme heat can kill," Mr Smith said.
"Make sure you take plenty of rest in the shade and drink water and the main thing is to make sure you don't get dehydrated," Mr Smith said.
"ACT ambulance staff are checking resources on a day-to-day basis and we're increasing resources to make sure we deal with a potential surge in workload."
Senior forecaster at the Bureau of Meteorology Rosemary Barr said the smoke that has been choking Canberra would continue for several days, coming in during the evenings.
"The easterly winds have been bringing over significant smoke into Canberra," Ms Barr said.
"There's also been smoke building up over western NSW and westerly winds are pushing that through but it's not as concentrated."
Ms Barr said the large amounts of smoke could see the temperature forecast for Canberra be one or two degrees lower than previously forecast, but hot and dry conditions were expected for several days.
"We'll continue to see smoke impact in the ACT as long as there's still significant bushfires still around," she said.
Wednesday is expected to reach a top of 37, before rising to 40 on Thursday with some late smoke.
Temperatures will drop to 38 on Friday before rising to 42 on Saturday.