Every day, new stories about how people and wildlife have been impacted by bushfires across Australia emerge.

And with so many fires burning across multiple states, there is no sign of them abating.

NSW Rural Fire Service (RFS) Commissioner Shane Fitzsimmons has emphasised that it will take weeks to put out these fires, even with several days of milder weather forecast for the most affected areas.

But why is this the case, and why can't more be done on days of lower temperatures and little wind?

Dry, changeable conditions

In the past, firefighters could be confident that a fire would eventually run up against wet ground or plants, which would slow its progress.

Without dry fuel, it would founder and die.

Equipment similar to common garden tools can be used to remove fuel from a fireground. ( Supplied: NSW RFS )

But this fire season has come amid a period of severe drought and unprecedented weather conditions, driven by climate change.

That means both drought and strong, gusty winds in combination.

Brian Williams, who has worked as an RFS volunteer and professional firefighter for more than 50 years, said the weather patterns were making it impossible to extinguish the large blazes burning in multiple locations.

"I've never seen fire burn so quickly — because we're in such a dire drought there is no moisture on the ground," Mr Williams said.

"And that means when a fire runs through it doesn't lose any energy in igniting fuel in front of itself. It just keeps picking up speed and growing bigger and higher and faster and hotter."

Waterbombing only works in some areas

Waterbombing can be of limited use in some conditions. ( ABC News: Nathan Morris )

Viewed from the ground or via videos from the scene, waterbombing planes appear to be dropping mammoth volumes of water onto the fires.

But several factors impact their efficacy, including the fact that the water usually fails to fall any further than the tree-tops, when dropped on fires burning in wooded areas.

"Our eucalypts are such a big heavy tree, we have heavy canopy, lots of leaf and lots of branches and the water will just not penetrate through," Mr Williams said.

"By the time the water hits the canopy, it's a very, very mild amount of water hitting down onto the ground."

As a result, any waterbombing efforts are directed towards those areas where firefighters are trying to protect property.

Where the Shark Creek fire has been burning in northern NSW, it's a little different.

There, the fire has been burning in peat underground and waterbombing has only managed to suppress the fire for a few days at most.

"We just can't put enough water out there [in] large-scale waterbombers, even the supersize waterbombers — they can't carry enough water," Mr Williams said.

Fighting fire with fire: backburning makes a blaze bigger

A fire burning at Monastery in Penrose, NSW, on January 10. ( ABC News: Brendan Esposito )

The main strategy used by firefighters now is to manage the edges of each fire, Mr Williams said.

"Because of the sheer size of them, you just cannot get in and put them out," he said.

When weather conditions ease, backburning is a key tool.

"I think this week we're forecast to have some very good days, so that gives the opportunity then for planning to go ahead, for getting in and back-burning as much as possible, to try and contain it to hard roads," he said.

"And that may be along the Kings Highway or major forestry trails, and that then prevents large fire runs on those real, hot windy days.

"If we can take fuel away we're making the fire bigger but we're reducing the possibility of the fire breaking containment lines."

Backburning is conducted on days of milder conditions around the edges of active fires and is different to hazard reduction burning, which is done during colder seasons to mitigate risk once it becomes hotter.

But hazard reduction burning has not been effective in every case, due to the catastrophic conditions, Commissioner Fitzsimmons said last week.

"We've had plenty of reports in the recent emergency of the fires just racing through areas that had had hazard reduction burns. There was very little effect from having hazard reduction burns being done," he said.

The fires' impacts have been felt by people and wildlife alike. ( ABC News: Matt Roberts )

Firefighter safety

Fires are indiscriminate about where they burn and often find their way into inaccessible places.

This season's unpredictability meant that was even more of an issue for those battling each blaze, Mr Williams said.

Many fires have been burning in places that are either short on escape routes, or in areas of tough terrain where the risk of injury is high.

"Firefighter safety is paramount," Mr Williams said.

"We have a rule and we go out to fight fires to save people's lives — and the general public and the firemen's lives comes before anything else.

"Going into these remote areas, we know we can get in, but if you look at the worst-case scenario, a weather change, can they get out safely?"

The safety of firefighting personnel is the main priority for authorities, Mr Williams said. ( Supplied: DFES incident photographer Evan Collis )

Instead, they focus on breaking the fire down into manageable sections, favouring those parts that are more easily accessible by way of paths such as fire trails.

"We look at areas that we can attack and try and, with planning, break the fire down into grids that you work on," he said.

"They're the areas that you attack when the conditions are right, so you can try and mitigate fire spread in those parts of the fire."

Ensuring personnel get the rest they need is also a consideration for authorities.

Mr Williams said all personnel, including firefighters, would be suffering from fatigue after so many weeks of bad weather.

Long-term heavy rain is our best hope

Bushfires burning in heavily wooded or high areas of forest can be inaccessible for firefighters. ( ABC News: Mitch Woolnough )

The message from fire authorities is clear: only heavy, consistent rain will put an end to these megafires before the bushfire season ends.

Even in the Tallaganda National Park, where the blaze first started in November, flames and embers still sometimes flare up.

"We just need a couple of weeks of constant rain," Mr Williams said.

Bushfire Science Associate Professor Geoffrey Cary of the Fenner School of Environment and Society agreed, saying the drought was a key factor in the scale and ferocity of the fires.

"A key reason these bushfires can't easily be extinguished during milder fire weather is the severity of the drought combined with thousands of kilometres of the perimeter," he said.

He said the previous three years of low rainfall had exacerbated those conditions.

"Australia experiences extensive drought from time to time. Notable for this drought is that winter rainfall has been at very low levels for the last three years and its during this period that moisture content typically recharges," he said.

"What is critical is the capacity of fire agencies to extinguish fires during milder weather conditions to limit the extent of the area burned."