Wyo. Stat. § 31-5-302
Whenever the superintendent determines upon the basis of an engineering and traffic investigation, or in the event of a vehicle or weather emergency, that a maximum speed greater or less than that authorized herein is safe and reasonable under the conditions found to exist at any intersection or other place or upon any part of the state highway system, the superintendent, except as provided for in W.S. 31-5-303(b), may determine and declare a reasonable and safe maximum limit thereat, which shall be effective when appropriate signs giving notice thereof are erected and which shall not exceed eighty (80) miles per hour on interstate highways. The maximum speed limit may be declared to be effective at all times or at such times as are indicated upon the signs and differing limits may be established for different times of day, different types of vehicles, varying weather conditions, and other factors bearing on safe speeds, which shall be effective when posted upon appropriate fixed or variable signs. This section does not grant power to the superintendent to declare statewide or countywide maximum speed limits but grants power to declare maximum speed limits for the public safety in localized geographic areas.
W.S. 31-5-302