A total fire ban is in place in the ACT with emergency services facing extreme conditions not seen in a decade .
Temperatures in the ACT are forecast to top 38 degrees Celsius with winds reaching 50 kilometres per hour.
ACT Rural Fire Service Chief Officer Andrew Stark says there could be fires in the Brindabella Ranges not seen since the 2003 Canberra bushfires.
"So people need to be aware and ring triple-0 and report any fire that they see that's unattended by a fire truck," he said.
A helicopter with infrared equipment searching for flare-ups in the Namadgi National Park south of Canberra has found a handful of hot spots this morning.
Fire crews have been battling three fires in Namadgi since lightning strikes at the weekend.
Twelve hot spots were found within the containment lines at Mount Ginini and four were found at Sentry Box. There were none at the Rendezvous Creek fire site.
Mr Stark says the winds could pick up to 100 kilometres an hour in the mountains.
"So there's four tanker crews, some light units and then the helicopter supporting them at the Ginini fire," he said.
"We're preparing to winch people into Sentry Box, so there could be another crew of six people on the ground. That's as many people as we can get safely to that fire under these conditions.
No other fires have been reported in the ACT at this time.
Authorities are urging people to avoid bushland.
Most ACT nature reserves have been closed until Saturday, including Namadgi National Park, Tidbinbilla Nature Reserve, Googong Foreshores and Kowen Forest.
The lower Molonglo river corridor and Mulligans Flat Woodland Sanctuary are also closed.
Boboyan Road and Brindabella Road remain open to through traffic.
"With the very bad fire weather expected in the coming days, closing Namadgi, Tidbinbilla, Googong Foreshores and Kowen Forest will enable staff to concentrate on fire suppression efforts, as well as ensure visitors are out of harm's way should conditions deteriorate," said Daniel Iglesias from ACT Parks and Conservation.
The Australian National Botanic Gardens is closed beyond the cafe.
A blaze near Gunning north of Canberra is also under control after burning out more than 70 hectares.
A firefighter suffered severe burns in that fire yesterday and was airlifted to Sydney for treatment.
The ACT Government is urging horse owners to activate their fire plans now and ensure their animals are in a safe location.
If necessary, horses can be taken to Exhibition Park in Mitchell.
Horses taken to EPIC must not be left unattended, and owners must take water and feed buckets with enough feed for 24 hours.
Owners are warned not to make evacuation decision at the last moment.