This snake inhabits a wide diversity of habitats, from prairies and arid basins to wooded mountains (Lowe et al. 1986, Degenhardt et al. 1996, Hammerson 1999, Werler and Dixon 2000, Stebbins 2003, Campbell and Lamar 2004, Werner et al. 2004). It is primarily terrestrial but sometimes climbs into trees or shrubs. When inactive, it occupies mammal burrows, crevices, caves, or similar secluded sites. Pregnant females may congregate near the winter den until parturition (Gannon and Secoy 1985, Graves and Duvall 1992).

As defined by Crother et al. (2003), following congruence of Pook et al. (2000), Ashton and de Queiroz (2001), and Douglas et al. (2002), this species encompasses only the ranges of subspecies viridis and nuntius of traditionally defined C. viridis. In other words, the range extends from southern Alberta and southern Saskatchewan in Canada, to the northern fringe of northern central Mexico, west to Idaho, Wyoming, Colorado, and extreme eastern Arizona, east to the Dakotas, western Iowa, Nebraska, central Kansas, central Oklahoma, and western and central Texas in the United States (Stebbins 2003, Campbell and Lamar 2004). The ranges and relationships of Crotalus oreganus and Crotalus viridis in the Four Corners region and in northwestern Colorado need further clarification (Hammerson 1999; Brennan and Holycross, 2004). Its elevational range extends from about 100 m asl near the Rio Grande (Campbell and Lamar 2004) to at least 2,895 m asl (9,500 feet) in Colorado (Hammerson 1999).

Many occurrences of this species are in protected areas.