Large parts of southern Australia face above-average fire risk this season, according to the Bushfire Co-operative Research Centre.

Abundant grass growth and high temperatures since January have led to a build-up of fuel in grasslands and dry forests.

The areas most at risk are not as extensive as last year, but even normal conditions can produce fast-running fires, the centre warns.

More than 1200 firefighters tackled four major blazes in western Sydney and the Blue Mountains last week. At least one home was destroyed, along with property including cars and sheds.

One of the fires is thought to have started when a hazard-reduction burn got out of control and another by powerlines brought down in high winds. Temperatures had risen to 31.6 degrees.