Hawke's Bay Today files show restricted fire season notices in place most years by the second week of November, with closed-season notices sometimes in place by Christmas.
Cooper said more advanced technology and methods have enabled better means of assessing when fire restrictions should be imposed.
But rainfall this November and December has resulted in what farmers and weekend lawn-mowers have been calling exceptional late-December grass and other vegetation growth.
Cooper said that with the high temperatures this week, the threshold for putting restrictions in place, assessed weekly, is close and a restricted fire season notice could be introduced "in 7-to-10 days".
He said the growth would quickly dry out, elevating the risks of rapid spread of fire.
"There's going to be significant growth," he said. "You must have a means of putting it out," he said. "If you haven't – don't light it."