The conditions across NSW on Sunday were described as the "worst possible" in recent history as winds swept through areas already scorched from a record-breaking heatwave.

Two out-of-control fires created devastation for small communities.

The tiny town of Uarbry, 120 kilometres east of Dubbo, was effectively wiped out by a fire that also destroyed properties in nearby Cassilis. And a fire around Pappinbarra, west of Port Macquarie, destroyed at least three properties.

However, Rural Fire Service spokesman Ben Shepherd said it was a matter of pure luck that the worst fires flared in parts of the state that were not heavily populated.

"We were extra lucky we didn't see fires through parts of the lower Hunter Valley," Inspector Shepherd said. "Whilst they didn't impact on majorly populated areas, the fire activity was still extraordinary."

Hundreds of thousands of text message warnings were sent to residents across NSW on Sunday, resulting in a level of preparedness rarely seen before.

"A few people didn't think that was necessary but, by far, the majority knew and understood the period we were leading into warranted such messaging," he said.

"I think that, in the end, we have to consider that that was a contributing factor both for the community understanding the risk on the day and also being more vigilant and ... prepared."

The Rural Fire Service has amassed one of the largest and most flexible firefighting forces in the world.

On Sunday, as conditions started to relax in southern NSW, crews moved further up into areas that were experiencing the worst.

Strike teams responded to initial calls while other trucks fell into communication roles, warning the public ahead of fires that were out of control.

Such was the dedication of volunteers, two RFS members lost their properties while out fighting fires including a local captain at Uarbry who was helping a neighbour.

"If you were to ask them, would they change anything, they understood the need was there to go fight fires," Inspector Shepherd said. "But unfortunately the outcome is heartbreaking."

RFS commissioner Shane Fitzsimmons praised the "extraordinary effort" of firefighters.

"What they saved yesterday will far outweigh the losses that we report today," he said on Monday.

"I know that is cold comfort for those who have lost so much and I don't mean any disrespect or being insensitive, but we cannot take away from the amount of property, people, livelihoods that have been saved under yesterday's conditions."

More than 2500 firefighters and 50 aircraft were mobilised to battle 200 blazes on Sunday.

Cooler temperatures on Monday helped crews gain the upper hand before more hot and dangerous conditions later in the week.