Idaho Code § 39-1329
The board shall meet regularly once each month at a time and place to be designated by the board. Special meetings may be held as often as the needs of the district require on notice to each member of the board. A majority of the members of the board shall constitute a quorum at any meeting. Any vacancy of an elected member on the board shall be filled by the remaining members or member of the board, the appointee to act until the next biennial election, when the vacancy shall be filled by election. If the board shall fail, neglect or refuse to fill any vacancy within ninety (90) days after the same occurs, the board of county commissioners of the county in which said district is situated shall fill such vacancy. In the case of a vacancy on the board of an appointed member, a majority of the board shall determine whether to fill the vacant position.
Idaho Code § 39-1329