Okla. Stat. tit. 63 § 685.4
Whenever a natural or man-made disaster or emergency occurs in the United States, and in the event that the Governor, for any of the reasons specified in Article VI, Section 16 of the Oklahoma Constitution, is not able to exercise the powers and discharge the duties of the Governor's office, or is unavailable, and in the event the Lieutenant Governor, President Pro Tempore of the Senate, and the Speaker of the House of Representatives be for any of the reasons specified in the Constitution not able to exercise the powers and discharge the duties of the office of Governor, or be unavailable, the State Auditor and Inspector, Attorney General, State Treasurer, Superintendent of Public Instruction, Commissioner of Labor, and members of the Corporation Commission in the order of their election districts, shall each in the order named, if no officer higher in the enumerated order is available, exercise the powers and discharge the duties of the office of Governor until a new Governor is elected and qualified; provided, however, that no emergency interim successor to the aforementioned offices may serve as Governor.
Okla. Stat. tit. 63, § 685.4