Incident controller Ross Kerr said people think the forest is wet, but it's not.
He said a total fire ban is in place and a fire ban means no fires at all.
Meanwhile, spontaneous combustion is the likely cause of a hay stack fire in Canterbury.
Rural fire-fighters were called to a Swannanoa property north of Christchurch at about six last night.
Senior station officer Tristan Roberts said engines from Kaiapoi, Pines beach and Brooklands took more than an hour to bring it under control.
He said the fire is not suspicious.
"The probably cause is spontaneous combustion which is where high-moisture hay stacks can have a chemical reaction that builds heat,'' he said.
"Hay basically insulates so the larger the hay stack, the less cooling effect there is to offset the heat.''
Mr Roberts said farmers are giving into the temptation to bail hay when it is a bit too damp and this is one of the risks.
He urged farmers to check the temperature of their stacks.
