SOUTH Australia is bracing for a day of high bushfire danger tomorrow with temperatures in the 40s and strong winds forecast.

The Bureau of Meteorology said Adelaide would have a top of 42C with northeasterly winds to 35km/h ahead of a cooler change set sweep across the city later in the day.

In the Riverland the mercury was expected to hit 44C at Renmark while Ceduna, on the west coast, was forecast to have 45C along with Wudinna, on Eyre Peninsula.

The Country Fire Service listed the bushfire risk as extreme in six districts and severe in the remaining seven.

If the mercury reaches 40 on Thursday it will be Adelaide's fifth day above that mark so far this summer.

On Friday the bureau has forecast some light morning showers for the city with a top temperature of a more comfortable 26C.