SYDNEY is set to swelter through another heatwave this week with six days of extreme heat on its way, including three consecutive days over 40 degrees.

The mercury is expected to top 35 in the west today before a high of 36 tomorrow and 38 on Wednesday.

Things get even worse on Thursday when temperatures are expected to hit 41 out west before a stifling 43 on Friday and 40 on New Year’s Eve.

It will be slightly cooler towards the city and east today and tomorrow — with highs of 29 expected today and tomorrow and 30 on Wednesday — but the mercury will rise to 38 on Thursday and 36 on Friday.

Those in the city will see out 2016 with a possible shower and 33 degrees.

media_camera It’s going to be VERY hot this week. Picture: Dylan Robinson

The extreme temperatures will provide a headache for the Rural Fire Service, but high levels of humidity and favourable wind conditions will hopefully help keep the risk down.

But the heat means that bushfires are a real danger, RFS spokesman John Redman told The Daily Telegraph.

“Whenever there are hot conditions, anything can happen,” he said.

“We have 74,000 volunteers right across NSW and every brigade will be manned and if something does happen they will respond immediately.”

media_camera A heatwave will hit parts of NSW this week. Picture: Bureau of Meteorology

There are 28 fires currently burning across the state and the heatwave bearing down on the state, the RFS warned anyone thinking of lighting a fire to think twice.

“If you’re inclined to do that sort of activity, it’s never been easier to get caught,” he said.

“The brutal truth is these aren’t the smartest of people — they tell their mates, they takes photos of it and they try and claim it’s a cool thing to do.

“But in reality you are putting lives at risk, you’re putting properties at risk and when you’ve got people who are volunteers — or professional fire fighters — the fact that you would put those people in that situation purely just to get your rocks off on lighting fires is unbelievable.”

BOM - Extreme heatwave forecast over Christmas period BOM - Extreme heatwave forecast over Christmas period

Originally published as Heatwave about to hit Sydney