Severe bushfire risk for South Australia

South Australia is bracing for a day of severe bushfire risk with the Adelaide Hills area of particular concern.

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

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

The Country Fire Service says thousands of cycling fans are expected to flock to the hills to watch the opening stage of cycling's Tour Down Under.

CFS state co-ordinator Leigh Miller says people moving through the area need to understand the risks and be bushfire aware.

"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."