Catastrophic bushfire conditions have been declared across two South Australian districts, the first this summer.
The declarations for Saturday apply to the lower Eyre Peninsula and Yorke Peninsula with temperatures set to surge into the mid-30s and winds to increase ahead of a cooler change.
"If a fire takes hold under the forecast conditions tomorrow, it will be fast-moving, it will be dynamic, it will be very difficult for ground and aerial resources to control," Country Fire Service Chief Officer Brett Loughlin said.
"It will present a clear risk to lives, property and livelihoods in those communities."
In response, the CFS has positioned four firefighting aircraft on Eyre Peninsula, in the mid-north and in the Adelaide Hills.
A large air tanker has also been secured from Victoria and will be stationed at the Edinburgh RAAF base in Adelaide.
Mr Loughlin said farmers in the high-risk areas were strongly advised not to undertake any high-risk activities on Saturday, including the movement of heavy machinery through paddocks as part of harvesting crops.
He said the late harvest this year, because of the wetter-than-usual spring, meant there was a greater risk than usual from farming activities.
Meteorologist Jonathan Fischer said Saturday's spike in the fire risk was being driven by strengthening northerly winds and rising temperatures ahead of the gusty westerly change.
The wind shift would add to the fire risk.
However, Mr Fischer said no lightning was expected.
From Sunday, temperatures are forecast to be milder with the chance of showers, with cooler days expected to extend into next week.
Mr Loughlin said while Saturday's catastrophic conditions were the first this summer, they were inevitable.
"Though we've had a slow start to the season there is not a single summer in South Australia where there's not a threat to lives and property from fire," he said.
