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."

The heat will be more intense in western Sydney, with a maximum temperature of 36 degrees forecast for Penrith and Richmond on Saturday, and 32 degrees for Sunday.

While the ski season is still under way, the state is also on track to record its first 40 degree day in September, with Bourke, Brewarrina and Tibooburra all forecast to hit the record temperature on Saturday.

"There's nowhere in NSW, since records began, that have reached 40 degrees in September," Mr Brittain said.

The high temperatures are concerning firefighters - a "vast area" of the state will have very high fire danger by the weekend, with some areas suffering "severe" risks, according to Ben Shepherd, a spokesman for the NSW Rural Fire Service.

Sydney could also achieve another dubious record, with its driest September since 1882.

September is traditionally the city's driest month, with an average of 68mm of rain.

But Mohammed Nabi, duty forecaster with the Bureau of Meteorology, said the city had recorded just 0.2mm of rain, which fell on September 14th, and "it was just a light sprinkle".

"All the other days have been rain-free," he said.

Sydney's wettest September was in 1879 when it recorded 355mm, while just 2.1mm was recorded in 1882, Mr Nabi said.

Mr Nabi said the city will come close to beating its low rainfall record for the month depending on what happens next week - the Bureau of Meteorology's latest forecast suggests a 40 per cent chance of showers next Thursday.

"It will get really close either way - either coming under or just over," he said. "You could count it as one of the driest Septembers."

The dry, warm conditions have not affected the paper daisies in bloom at the Australian Botanic Garden at Mount Annan.

Jimmy Turner, the director of horticulture at the Australian Botanic Garden, said the flowers had bloomed "pretty much on time this year".

"The plants are actually quite well-adapted and love the hot temperatures as they are from the hot, dry climate of Western Australia," he said. "Not an ideal climate for us humans, but the Australian plants always do quite well."

Weatherzone is owned by Fairfax Media, publisher of this website.