Australian comedian Celeste Barber's fundraiser has raised more than $4million for The Trustee for NSW Rural Fire Service and Brigades Donations Fund - and it's far from over.

The Facebook donations page was set up on Friday and has been widely shared across the social media platform by those wanting to help.

As of Saturday afternoon, on a day of unprecedented fire danger in NSW - $4,083,599 has been raised to go towards the important cause.

"Want to join me in supporting a good cause?" Barber wrote on the Facebook page.

"I'm raising money for The Trustee for NSW Rural Fire Service & Brigades Donations Fund and your contribution will make an impact, whether you donate a lot or a little.

"Anything helps. Thank you for your support."

Worldwide support

People around the world have jumped at the chance to be able to help out those battling the catastrophic blazes Australia has faced this bushfire season.

"Donated from Somerset, England. Shared via Facebook and Instagram and some of my friends have shared too. It is great to see the snowball effect working," Lizzie Tucker wrote.

"Donated from BC, Canada. Australians came to fight our fires in 2017 and 2018 and we are forever grateful!" Emmanuelle Claws said.

"Donated from Pittsburgh, Pennsylvania, U.S.! Sending you love!" Lyndsey Marie said.

Chevron Right Icon 'Australians came to fight our fires in 2017 and 2018 and we are forever grateful!'

Barber also shared some "terrifying" images taken from her mother-in-law's house, where the effects of the fires can be seen first hand.

"This is my mother-in-law's house. It’s terrifying. They are scared. They need your help. International donations can be made via the link in my bio," she wrote in the Instagram post.

The incredible effort comes on a day where NSW is preparing for the worst, as dangerous winds and heat travel towards dozens of towns.

Extreme fire danger has been predicted for a massive six fire districts across the state's southeast as well as the ACT.

More from 7NEWS.com.au on the bushfire crisis:

Severe conditions are also forecast for the Hunter, Sydney and the central ranges.

If you'd like to donate to Celeste's fundraiser, you can do so here.

In the video below: NSW braces for predicted bushfire onslaught