The blaze was a warning to others, she added. She had had a fire but believed it was out because there was no more smoke.
"A few hours later a wind came up, I smelled smoke ... too late," she wrote.
"This happens so fast. I'm lucky to have my life, my house, and only a relatively small area of charred ground. Sadly a friend of mine was not so lucky a few months back. Beware, fire is ferocious."
Ms Watson said Northland was already tinder-dry, and urged anyone planning a fire to take precautions by clearing the area around the fire, having lots of water on hand and making sure the it was properly extinguished.
"If in doubt don't light the fire, ring the local fire brigade to see if it's okay," she said.
Principal rural fire officer Myles Taylor earlier said he was amazed the house had survived. He urged Northlanders to take extreme care with fires, especially in the current strong winds.
The Rural Fire Authority would require fire-starters to pay firefighting costs this summer. Costs could run into many thousands of dollars, especially once helicopters were required. Each chopper costs around $2500 an hour.