Hardiness zone maps are not very detailed and do not accurately show hardiness zones in much of the West due to elevation and microclimate variations. The table below includes hardiness zones using the USDA temperature ranges but calculated with local weather data gathered from 1990 to 2019. Hardiness zones are included for most weather stations in Utah and for several stations in each of the surrounding states. The data was provided by Utah Climate Center at Utah State University and calculations were done by Gabrielle Harden, Forestry Extension. To find your zone, find a station near you that is similar in elevation and other factors. A station designation like Telluride 4WNW indicates that the station is located 4 miles west-northwest of Telluride, Colorado.
Though this table gives more detailed coverage, these zones should be used with caution. Slight differences between weather station conditions and your site could mean large differences in the hardiness zone value. Also, these are means rather than absolute minimums, so if your area occasionally gets much colder than the mean temperature in the table then you might consider going with a lower hardiness zone. These averages may vary from those in the official USDA map due to the difference in time periods for used data (1990 to 2019 vs 1976 to 2005). Cache County in Utah, for example, shows mostly at zone 5b on the map but the figures below for Cache County are mostly zone 4b. When in doubt, or if you are worried about losing a plant, use a more conservative zone value (lower zone number)
Zone temperature designations were determined using the USDA Plant Hardiness Zone Map.