5 C.F.R. § 340.402 – Seasonal employment.

(a) Appropriate use. Seasonal employment allows an agency to develop an experienced cadre of employees under career appointment to perform work which recurs predictably year-to-year. Consistent with the career nature of the appointments, seasonal employees receive the full benefits authorized to attract and retain a stable workforce. As a result, seasonal employment is appropriate when the work is expected to last at least 6 months during a calendar year. Recurring work that lasts less than 6 months each year is normally best performed by temporary employees. Seasonal employment may not be used as a substitute for full-time employment or as a buffer for the full-time workforce.
(b) Length of the season. Agencies determine the length of the season, subject to the condition that it be clearly tied to nature of the work. The season must be defined as closely as practicable so that an employee will have a reasonably clear idea of how much work he or she can expect during the year. To minimize the adverse impact of seasonal layoffs, an agency may assign seasonal employees to other work during the projected layoff period. While in nonpay status, a seasonal employee may accept other employment, Federal or non-Federal, subject to the regulations on political activity (part 733 of this title) and on employee responsibilities and conduct (part 735), as well as applicable agency policies. Subject to the limitation on pay from more than one position (5 U.S.C. 5533), a seasonal employee may hold more than one appointment.
(c) Employment agreement. An employment agreement must be executed between the agency and the seasonal employee prior to the employee's entering on duty. At a minimum, the agreement must inform the employee:
1. (1) That he or she is subject to periodic release and recall as a condition of employment,
2. (2) The minimum and maximum period the employee can expect to work,
3. (3) The basis on which release and recall procedures will be effected, and
4. (4) The benefits to which the employee will be entitled while in a nonpay status.
(d) Release and recall procedures. A seasonal employee is released to nonpay status at the end of a season and recalled to duty the next season. Release and recall procedures must be established in advance and uniformly applied. They may be based on performance, seniority, veterans' preference, other appropriate indices, or a combination of factors. A seasonal layoff is not subject to the procedures for furlough prescribed in parts 351 and 752 of this title. Reduction in force or adverse action procedures, as applicable, are required for a seasonal layoff that is not in accordance with the employment agreement, for example, if an agency intends to have an employee work less than the minimum amount of time specified in the employment agreement. However, an agency may develop a new employment agreement to reflect changing circumstances.
(e) Noncompetitive movement. Seasonal employees serving under career appointment may move to other positions in the same way as other regular career employees.