Temperatures are expected to hit 39 degrees in Sydney and 41 degrees at Penrith on Sunday. Credit:Jessica Hromas

Sydney, if you thought Saturday was hot, keep your swimmers out for Sunday.

The mercury soared across the city on Saturday, reaching 31.9 degrees in the CBD around 1.30pm. Out west, the temperature hit the mid-30s, reaching 35 degrees in Richmond and 36.8 degrees in Campbelltown around 4pm.

But there's little relief in sight yet - Sunday is set to be even hotter, with 39 degrees predicted for the CBD and most of the greater Sydney region.