A temporary sign or banner, not in excess of 35 square feet in area, shall be permitted to announce or advertise, no more than 30 days in advance, such temporary uses as fairs, carnivals, seasonal agricultural events, circuses, revivals, sporting events, flea markets or any public, cultural, charitable, educational or religious event or function, including message of congratulation or commemoration. Such sign shall be removed within 15 days after the special event.