All signs of a temporary nature, including advertising banners, pennants, ribbons, streamers, spinners or similar moving, fluttering or revolving devices, shall be allowed, (except as otherwise provided by this section), and shall be permitted for a period not exceeding six weeks prior to the activity or event, nor exceeding four days after the activity or event. Such signs shall not exceed 16 square feet in business or industrial districts nor eight square feet in residential districts, nor be attached to fences, trees, rocks or other parts of a natural landscape, nor be placed in a position that will obstruct or impair traffic or in any manner create a hazard or disturbance to the health, safety and welfare of the general public.