Section 28B. When the forest fire hazard, as determined by the director of the division of forestry, according to the United States Forest Service standard of classification of fire danger, or its equivalent in any future classification, shall reach a burning index of fifty or higher, the forest warden, within the limits of funds appropriated for such purposes, may, and upon the order of the forester shall cause the forests of such town to be patrolled for the prevention of such fires. The cost of such patrol, if ordered by the forester, shall be paid by said town, subject to reimbursement by the commonwealth, if the valuation of such town does not exceed one million two hundred and fifty thousand dollars, as if incurred for the extinguishment of forest fires as provided in section twenty-four.