Actor Russell Crowe has spearheaded a $400,000 donation to the NSW Rural Fire Service, after pledging to match the price of a hat he auctioned off to raise money for the firefighters.

The battered baseball cap fetched $US68,000 in a Twitter auction that ended on Friday morning (AEDT) – with the highest bid coming from Atlassian co-founder Mike Cannon-Brookes and triggering a cascade of high-profile six-figure donations to the RFS.

Mr Cannon-Brookes said he would match Crowe’s donation, with the pair each committing to give $5000 each to 20 RFS brigades.

On top of that, Mr Cannon-Brookes said later on Friday that his Atlassian co-founder, Scott Farquhar, and Ryan Smith, the chief executive of US software company Qualtrics, would each chip in their own $100,000 donation.

“You’ve started something amazing here,” Mr Cannon-Brookes tweeted to Crowe.

“Your hat has now generated $400k in donations in 24h to help tired, exhausted fireys!”

Crowe, whose Nana Glen property near Coffs Harbour was hit by bushfires a few weeks ago, had earlier pledged to triple the highest bid on the “slightly worn” South Sydney Rabbitohs cap.

On Friday, he confirmed he would match Mr Cannon-Brookes’ offer – and donate the cash to the firefighters.

Hey @russellcrowe @NSWRFS – you've started something amazing here.

Unasked, both @scottfarkas and @RyanQualtrics are matching the $100k as well. Total legends both of them! 👏🏻 Thank you both!❤️

Your 🧢 has now generated $400k in donations in 24h to help tired, exhausted fireys! https://t.co/Wp7W2lQbD7

— Mike Cannon-Brookes 👨🏼‍💻🧢🇦🇺 (@mcannonbrookes) November 29, 2019

So… delivered 19 cheques to RFS Captain John Lardner, a total of $105k because I cant count apparently,
haha all good@NSWRFS pic.twitter.com/QlCEXMBlm6

— Russell Crowe (@russellcrowe) November 29, 2019

Crowe, who on Tuesday released video footage of a NSW forest scorched by bushfires and clean-up efforts in the area surrounding his property, earlier said the Rabbitohs hat would be “signed and personalised to the highest bidder”.

He was not in the country when the bushfires hit his Nana Glen property, and said his family was safe.

The RFS welcomed the $400,000 donation – which Crowe started handing out on Friday.

“It’s reflective of the extraordinary generosity that we are seeing right across NSW and much further afield,” RFS commissioner Shane Fitzsimmons said.

He said the volunteer organisation would send the Oscar-winner an RFS hat to make up for the Bunnies one he auctioned.

25 mins to go to bid on this slightly worn hat pic.twitter.com/zhusnGPn42

— Russell Crowe (@russellcrowe) November 28, 2019

Meanwhile, the NSW bushfire crisis shows no sign of easing, with the RFS putting out a fresh warning for residents to prepare ahead of a hot and windy weekend.

On Friday afternoon, the RFS issued an emergency warning for the 4000-hectare North Black Range fire burning in the Tallaganda National Park area, west of Braidwood.

People in Bombay, Little Bombay and Farringdon Road north of Mount Creek were told to leave towards Braidwood if they aren’t prepared.

There are 146 bush and grass fires burning across NSW with 58 uncontained.

Six people have died and some 663 homes have been destroyed so far this bushfire season.

An RFS spokesman on Friday said overnight rain across northern NSW had hampered back-burning efforts but they would continue throughout the day.

Total fire bans are in place for the Monaro alpine, southern ranges, central ranges, north-western and southern slopes fire regions.

Those areas – along with the greater Hunter, greater Sydney, Illawarra-Shoalhaven, far South Coast, northern slopes and eastern Riverina regions – are experiencing very high or severe fire danger, as is the ACT.

• Read more: Smoke chokes Canberra as bushfires threaten to merge

The RFS tweeted on Friday: “Worsening conditions are expected tomorrow and over the coming week.”

Sydney’s air quality was “poor” on Friday, except for Liverpool and Parramatta where it was “very poor”. Air quality was “hazardous” in the Lower Hunter.

The environment department said air quality was problematic for those with illnesses such as heart or lung disease.

-with AAP