High fire risk for SA on Tuesday

South Australia is bracing for a day of severe bushfire risk with particular concern for the Adelaide Hills where big crowds are expected for cycling's Tour Down Under.

The fire risk has been declared severe in 10 districts and extreme in two more for Tuesday leading to total fire bans.

Adelaide is forecast to have a top temperature of 40C with many regional centres just as hot.

The Country Fire Service said riders in the Tour Down Under would pass through some areas of the Adelaide Hills that had experienced significant fires in recent years.

Fans moving through the region needed to understand the risks present in these locations and be bushfire aware, CFS state co-ordinator Leigh Miller said.

"We expect South Australians to be aware of fire risks, but visitors might not have an understanding of just how dry South Australia is," Mr Miller said.

"We're asking local spectators to consider their own actions, and also help watch over our guests from interstate and overseas."

Mr Miller said fires could start from a hot car exhaust parked in dry grass or from carelessly discarded cigarette butts.

The CFS will have two fire crews travelling with the race for each stage and police will direct traffic to park in areas where there is no roadside grass.

Temperatures across SA will be slightly cooler on Wednesday and Thursday, with a chance of showers, ahead of a more significant cool change on Friday.