A spark from a ride-on lawnmower blade hitting a stone may have start a grass fire that could have cost a Wendon farmer their home in Southland this afternoon (1 Jan), according to Fire and Emergency NZ (FENZ).

FENZ Southland Group Manager Timo Bierlin said what started as a grass fire quickly spread to a large hedge close to a farmhouse at Wendon about 3.30pm.

Six crews responded to help prevent the fire from reaching the farmhouse, sheds, farm implements and fuel supplies.

"It was a really close thing - the paint on the side of the house was bubbling and the guttering was destroyed," Bierlin said.

"We are really grateful to the volunteer firefighters who left their holiday activities to fight this fire."

Waikaka, Waikaia, Riversdale and Balfour Volunteer Fire Brigades attended the incident, with one crew remaining on site into the evening to ensure there were no flare-ups.

Bierlin said that people might not realise how easily the dry grass would catch fire.

With no significant rain forecast until at least the end of the week, Bierlin is urging people to think twice about activities - like mowing lawns - that could generate a spark and cause a similar fire.

"If you must mow, it’s best to do so in the early morning when the day is at its coolest."