Tex. Government Code § 433.001: PROCLAMATION OF STATE OF EMERGENCY.

On application of the chief executive officer or governing body of a county or municipality during an emergency, the governor may proclaim a state of emergency and designate the area involved. For the purposes of this section an emergency exists in the following situations:

(1) a riot or unlawful assembly by three or more persons acting together by use of force or violence;

(2) if a clear and present danger of the use of violence exists; or

(3) a natural or man-made disaster.

Acts 1987, 70th Leg., ch. 147, Sec. 1, eff. Sept. 1, 1987.