Firefighters raced to contain a major blaze on Monday before the return of strong winds and a heatwave, following the loss of 26 homes in the worst brushfire conditions in South Australia in 30 years.

The state fire service said properties were still at risk after nearly 12,500 hectares of scrub and farmland were razed in the Mount Lofty Ranges, east of Adelaide, at the weekend.

South Australia state Premier Jay Weatherill said that with cooler weather and calmer winds, it was now a race against time before dangerous conditions develop on Wednesday in the Adelaide Hills.