South Australia is about to sweat through its first heatwave of 2021, after a relatively mild start to its summer.

Authorities are warning South Aussies to prepare for several days of high temperatures before easing toward the end of next week.

Adelaide is predicted to hit a top of 32 degrees on Friday, with the mercury continuing to rise over the weekend.

Saturday will see a forecasted maximum temperature of 34 degrees, and it will only get hotter reaching 37 degrees in Adelaide by Monday.

The SES has warned South Australians to look out for falling trees, while authorities are reminding us to limit the amount of time we spend outside.

Relief is not expected to come until next Thursday when a cool change sweeps through the state, bringing with it sub-30 degree temperatures.