Signs which are intended to be displayed for a limited period of time only shall require a temporary sign permit. Application for temporary sign permits shall be made upon the form, as set out in Section 156.06, and the number of days for which the permit shall be effective shall be specified. However, the permit shall be valid for a period of time not to exceed thirty (30) days. No occupant shall be entitled to more than three (3) such permits in any calendar year; provided further, no more than one such permit shall be for a portable sign. A fee of $5.00 shall be charged for said permit, except for charitable and nonprofit organizations, which shall pay no fee. For the purposes of this chapter portable signs shall be considered to be temporary signs.