Whenever thawing or excessive moisture renders any section of any street, alley or other public thoroughfare within the municipality insufficient to bear loads of the weights prescribed in § 440.01, the Director of Public Safety, by order, may reduce the maximum allowable loads on such street, alley or any section thereof, but not by more than 50% of the maximum weights otherwise permitted, for and during such time as such condition of thawing or excessive moisture continues to exist.