The weather bureau says temperatures are started to fall across South Australia on Friday with the arrival of a south-westerly change.
The temperature reached 36.9 degrees Celsius at 11:00am and is now unlikely to reach the 41 degrees forecast reports the ABC.
Forecaster Megan Allen says the cool change arrived earlier than expected.
She said it was now thought the temperature would be in the low 20s by about midnight on Friday.
Six regions across South Australia have been given a catastrophic bushfire danger rating.
The Country Fire Service says it has contained more than 20 small fires across South Australia on Friday.
Acting chief officer Andrew Lawson says windy conditions have posed problems and firefighters remain on standby.