Three American firefighters and a South Coast resident have died during a horror NSW bushfire day as the state experiences its "darkest summer".
The death toll from NSW's unprecedented bushfire season has climbed to 25 after the body of a 59-year-old man was found in a home on the state's South Coast.
NSW Police Force confirmed the discovery of the human remains near the fire-ravaged community of Moruya on the state's south coast, on Friday afternoon.
It comes 24 hours after three US firefighters died when their aerial water tanker crashed northeast of Cooma and on the same day father and son Robert and Patrick Salway, who died protecting their home in nearby Cobargo, were buried.
The body was found earlier on Friday after concerns raised for a missing person on Thursday.
Little remains of the fire-destroyed home on Bumbo Road, Bodalla, south-west of Moruya.
"Detectives, police rescue and specialist forensic officers are currently on scene with the NSW Rural Fire Service, and a crime scene has been established," the NSW police spokesperson said.
A report will be prepared for the NSW Coroner.
The impact of the large fire near Moruya could be seen in videos posted on social media, with firefighters unable to save all the houses in the area.
Earlier, NSW Emergency Services Minister David Elliott on Friday said this season was the "darkest summer" in the state's history.
"I'm hoping we don't have a repeat next year, or the year after or for the next 10 years, but the reality is, we probably will," he told reporters in Sydney.
NSW Rural Fire Service Commissioner Shane Fitzsimmons said the state would "forever be indebted" to the sacrifice the three US firefighters made.
Plane owner and operator Coulson Aviation on Friday confirmed captain Ian McBeth, 44, flight engineer Rick DeMorgan Jr, 43, and first officer Paul Clyde Hudson, 42, were killed in the crash at Peak View.
The C-130 Hercules crashed just after dropping fire retardant along a ridge, Australian Transport Safety Bureau chief commissioner Greg Hood said, adding the kilometre-long crash site was "complicated" because it was in an active bushfire area.
ATSB investigators on Saturday will make the site safe by securing aviation fuel, the magnesium wheels and any unexploded oxygen bottles.
They will then locate the plane's voice recorder and take it back to Canberra "to see what the exchanges may have been in the cockpit during those final moments", Mr Hood told reporters on Friday.
Mr Fitzsimmons said hot, dry and windy conditions on Thursday resulted in flare-ups, fire spreading and new fire ignitions, as well as home losses.
Six firefighters battling the Clyde Mountain blaze on NSW's South Coast were injured when their truck rolled near Moruya.
"We've still got to get through the end of January, we've still got to get through February which is one of our months of summer and we still have to get through the end of the statutory bushfire danger period which might be extended - should the circumstances dictate - beyond March," the RFS boss warned on Friday.
While the three-month weather outlook for NSW does include some rainfall, Mr Fitzsimmons said it wouldn't exceed the average.
"We're not getting any strong signals of above-average rainfall, drought-breaking rainfall or fire season-ending rainfall."
Some 60 fires continue to burn across NSW but only one is at "watch and act" alert level.
Premier Gladys Berejiklian on Friday announced a state memorial service will be held on February 23 in Sydney to recognise the firefighters who have died this bushfires season.