Hardiness Zones

Hardiness Zones

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 1961 to 1990. Hardiness zones are included for most weather stations in Utah and for several stations in each of the surrounding states. Calculations were done by the Utah Climate Center at Utah State University. To find your zone find a station near you that is similar in elevation and other factors. A station designation like Klagetoh 12 WNW@ indicates that the station is located 12 miles west-northwest of Klagetoh, Arizona.

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. Overall the average zones in this table tend to be higher than those from the official USDA map in some of the colder locations. Cache County in Utah, for example, shows as mostly zone 4 on the map but the figures below for Cache County range from zone 2 to zone 6. When in doubt, or if you are worried about losing a plant, use a more conservative zone value (lower zone number).