Fire chief warning for 'deadly' grassfires

A fire chief has issued a stark warning for parts of eastern Australia, saying deadly grassfires could be on the way as areas dry out after flooding.

NSW Rural Fire Service Commissioner Rob Rogers said western NSW, parts of Queensland and the top of Victoria have all had a large amount of fuel build up after recent heavy rainfall.

"There's a massive amount of grass across those three states, and that's what we've got to deal with the remainder of this summer and obviously looking forward to then the following summer," Mr Rogers told AAP.

And he's called on farmers to be extra vigilant during harvest, with heavy machinery able to spark the fires.

The rural fire service issued a harvest safety alert to farmers in southern NSW this week as the danger increased.

"What really concerns us ... is that we're going to get in the second half of January, really hot days and strong westerly winds," Mr Rogers said.

"If we get fire starting like that with the level of growth out there and that growth is drying out, then those fires on those days will have the potential to be really destructive."

There have been 920 grassfires recorded in NSW since December 1, with 150 grassfires in NSW in the first five days of January.

While Mr Rogers says the bulk of the fires have been started by lightning, he reminded farmers using harvesters or other heavy machinery of the risks.

Over a 12-month period during 2021 to 2022 firefighters were called to 38 fires in NSW involving heavy equipment, 15 of those involved farming machinery like tractors, harvesters and pickers.

The fire commissioner also warned that fuel is building up faster than usual across the five million hectares burnt in NSW in the deadly 2019/2020 fires.

"I don't know whether it's the amount of rainfall that super soaked the soil, and then combined with the ash fertilising the soil ... but whatever the combination is that vegetation has grown back a lot faster," he said.

Mr Rogers said normally he wouldn't expect the areas to burn again for up to eight years, but he expects with the accelerated fuel build-up it's likely to be as soon as 2024.

"The concern is anecdotally that that vegetation is really growing at a considerably faster rate than it normally would."