The Bureau of Meteorology has forecast a top of 33 degrees and the fire danger will be severe.

A fire sparked under such conditions might be uncontrollable and move quickly, the Emergency Services Agency warned on Tuesday afternoon.

"Flames may be higher than rooftops," a spokesman said.

ACT ESA Commissioner Dominic Lane declared the ban for the territory from midnight until 11.59pm on Wednesday.

The following nature reserves and roads will be closed for the duration of the Total Fire Ban:

Tidbinbilla Nature Reserve, selected roads within Namadgi National Park including Apollo Road, Orroral Road, Old Mill Road, Warks Road, Mount Franklin Road and the Corin Dam Road, Googong Foreshores, Kowen Forest, Lower Molonglo River Corridor, Molonglo Gorge Nature Reserve, Mulligans Flat Woodlands Sanctuary and the Centenary Trail between Goorooyarroo Nature Reserve and Hall.

The Boboyan Road and Brindabella Road will remain open to through traffic as will the Tidbinbilla and Namadgi Visitors Centres.

Swimming areas at the Cotter and along the Murrumbidgee River such as Kambah Pool, Pine Island Point Hut and Uriarra Crossing will remain open.

Electric barbecues in Parks and Reserves including the National Arboretum Canberra and in Canberra's urban parks will be available, however, all gas barbecues will be turned off.

If a fire starts, the ESA advises you monitor the situation for any changes through the ACT ESA website www.esa.act.gov.au, the ESA Twitter and Facebook accounts, local media outlets or by calling Access Canberra on 13 22 81.