Sydney could record its driest September in more than 130 years, as temperatures climb into the 30s over the weekend.

A maximum temperature of 33 degrees is forecast for Saturday and 31 degrees on Sunday, following Friday's maximum of 28 degrees - well above the average maximum temperature for September of 20 degrees.

"It's quite exceptional heat for this time of year," said Graeme Brittain, a meteorologist at Weatherzone.

But Mr Brittain said there could be even hotter conditions: "There is potential for 35 degrees to be reached on Saturday should the sea breeze stay out."