Residents in four states are experiencing stifling conditions, with soaring temperatures over a long weekend in many parts of the country.

South Australia, Victoria, NSW and Tasmania are set to experience stifling conditions from Saturday to Monday.

The mercury is set to reach the low 40Cs in South Australia as severe heatwave conditions extend further west of the Eyre Peninsula over the long weekend.

The Bureau of Meteorology warned of a prolonged run of heat from Ceduna to Port Lincoln, Adelaide, the Barossa Valley, Narracoorte and Mount Gambier.

The state government activated a code red response late on Friday, with additional services available to people sleeping rough.

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Harness and greyhound races have been rescheduled in many instances.

Victoria’s Labor Day long weekend started with a total fire ban in five districts on Saturday before dangerous fire conditions are forecast to ease from Sunday.

The ban applies to the Wimmera, west and south Gippsland, central, north central and south west regions.

A severe heatwave is sweeping the state’s south, with the bureau warning it’s likely to be felt across a large area, including Melbourne, Ballarat, Horsham, Warnambool and Bairnsdale.

Melbourne is tipped to reach a top of 39C, while conditions are set to hit 40C in popular holiday towns along the Murray River, the southwest coast and Geelong.

Extreme and severe heatwave conditions have also hit Tasmania, with warnings or much of the state’s north and northeast.

Areas affected include Burnie, Devonport, Launceston, Richmond, Swansea and Whitemark.

There will be relief for King Island on Sunday but that’s not expected to flow through to the rest of the state until Tuesday.

Southern NSW is also experiencing a severe heatwave with temperatures set to reach the high 30Cs in several areas including the Riverina, Lower Western, Upper Western and South West Slopes.

Conditions are expected to ease from the middle of next week.

—AAP