Total fire bans have been implemented across half of the state with some parts expected to hit 40 degrees Celsius for the first time in September since records began.
Simon Lewis from the weather bureau says the unseasonal hot weather will be most obvious in the state's west.
"The highest we've recorded anywhere in NSW in September is 39.6C and there's a few places out in the far west, including Wanaaring and Wilcannia, that are a chance of getting 40C on Saturday," Mr Lewis from the Bureau of Meteorology said.
Temperatures in Sydney's west are expected to reach the mid-30s during Saturday and the NSW Rural Fire Service (RFS) said to expect total fire bans across Sydney and through the Hunter Valley on Sunday.
No 'meaningful' rain since June
The "unbelievably dry winter" will escalate the fire danger in the state, RFS Inspector Ben Shepherd said.
"The problem that we've got is that any fuel there is now just so dry, we really haven't seen any meaningful rain in some places since early June," he said.
"It is incredibly dry, that obviously gives us a fair amount of risk, that's what's elevating these fire dangers."
The RFS can only hope that the weather turns and wets the state.
"We'd love to see some rain, some meaningful rain. Up till such time, we need everyone to play their part," Inspector Shepherd said.
"Make sure that you're prepared. Make sure that you've got a plan."
Make a plan for the school holidays
Inspector Shephard emphasised that families moving around in the school holidays who might end up in bushfire risk areas to make their own plan.
"If you're starting to travel around for those school holidays, please, make sure you have a plan for the place you're visiting. Play your part, and hopefully we'll get through this season without too much fire activity and too much loss."
For people in severe and very high fire condition areas, the RFS has advised:
The peak body for emergency medicine warned the public to take care during the hot weather, drink plenty of fluids and avoid the sun.ABC