Robert Russell was sheltering from the rain in the family hay shed when he heard sparks and electricity - and saw the shed had been struck by lightning.
By the time he turned around there were flames behind him.
The Paradise Valley man said he ducked in from the heavy downpour when he heard alarming sounds.
"It (the fire) started off small and then just went boom, big straight away."
Robert tried to get a truck out of the area but then ran back to the house and told his father, Dennis, who called the Fire Service. He said the lightning would have hit the shed more than once and he did not see the storm coming.
"I didn't expect there to be a fire."
Robert had gone out for a walk and a hunt when out of nowhere it had started to rain heavily.
Farm owner Dennis Russell said the incident happened between 5pm and 5.30pm and the firefighters were there until about 1am.
Fire crews said the blaze was burning fiercely when they arrived. Two fire appliances and two tankers from Rotorua were needed to help put out the blaze. Dennis said one half of the barn was gone and there was quite a bit of hay in the shed behind the smoking debris, which was still smouldering yesterday afternoon.
There were at least 800 conventional bales and about 40 big round bales in the barn - the equivalent of about 1200 conventional bales.
"Nothing will be salvaged out of here."
Dennis had been working on and off yesterday to push the whole lot of wreckage away and out from the shed, which wouldn't take long once he got in there, he said.
"It's a matter of trying to get the bales out. "That's all you can do, and then stoke it up and keep burning it."
There was not much point in letting it go out now, he said.
He said the Fire Service was returning to pick up some equipment late yesterday and crews were also expected back this morning.
The farm owner said the storm was "right here" and he could see the lightning and hear the bangs across the farm and in the skies above his house.
Having a building struck by lightning was not something that had happened before, but
"years ago you used to get it on the copper wires".