Oregon Revised Statutes Public Officers and Employees § 240.425

Positions which occur, terminate and recur periodically and regularly regardless of the duration thereof shall be designated by rule, policy or procedure of the Personnel Division as seasonal positions. An employee who satisfactorily serves in a seasonal position the trial service period designated by the division or a delegated operating agency for the classification to which the seasonal position is allocated is entitled to permanent status as a regular seasonal employee.