The heat, expected to persist most of the weekend, has forced the cancellation of public events and sporting matches across the ACT, while schools are readying to protect students from the weather.

The ACT's total fire ban will apply on Friday and Saturday.

A severe fire danger rating is predicted on Friday as emergency services warn that fires starting in forecast conditions could be uncontrollable and fast-moving.

The mercury is expected to reach 41 degrees on Friday and Saturday, prompting schools to prepare for the extreme heat.

An Education Directorate spokesman said each school could implement its extreme temperatures management plan if needed.

This could include: Optimising natural ventilation, air movement and shade; using additional fans or coolers; easy access to water and increased use of water play; rotating classes through cooler areas on site; moving students to cooler areas of the school to minimise potential for heat stress; adjusting uniforms if required; and limiting playground access to shaded areas.

The Canberra Capitals will move their bout with the Bendigo Spirit from Saturday to Sunday, while an ACT Cricket spokeswoman said junior matches may be cancelled for the weekend, citing its rule to abandon fixtures in temperatures above 34 degrees.

Seniors matches would still go ahead, but they would accommodate for the weather with extra breaks, aiming to start play earlier at 9am, he said.

Canberra's Showtime in the City was set to run both Friday night and Saturday day, but the ACT government cancelled Saturday's activities with the show to run only from 4.30pm to 9.30pm on Friday evening in the city's centre.

Despite considering cancelling juniors league matches scheduled for the weekend, Basketball ACT made the call early on Thursday afternoon to treat games on a case-by-case basis, cancelling or halting matches if stadium temperatures sat at 40 degrees for an hour.

Ahead of the predicted spell of heat, the ACT Ambulance Service urged Canberrans to take appropriate precautions to protect themselves against the heat, including proper hydration and sun protection.

"Most importantly, stay in touch with your elderly and frail relatives and neighbours, and pay special attention to the health needs of babies and young children who can be adversely affected by the heat," chief officer Jon Quiggin said.

Acting senior meteorologist at the Bureau of Meteorology Andrew Haigh said the cool change expected to relieve most of south-east Australia on Sunday could come by mid-afternoon that day for cities like Sydney.

"The cool change which is scheduled some time Sunday or Monday, is coming up the coast faster than expected," he said.

However, because the ACT was situated inland, Mr Haigh added Canberrans might face a more gradual drop in temperatures as the wind brought the change in more slowly.

Temperatures are expected to drop to 32 degrees on Sunday.

"From Sunday to Monday, the wind will shift around overnight on Sunday, so then on Monday it will be light and variable," Mr Haigh said.

Bureau of Meteorology climatologist Karl Braganza said the run of hot days was unlikely to break records but noted they were unusual.

The nature reserves and roads closed for the duration of the total fire ban include: 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 Roa, 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 remain open to through traffic and the Tidbinbilla and Namadgi Visitors Centres will remain open.

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.