What Growing Zone Is Boulder?
Our records indicate the United States Department of Agriculture has given Boulder a growing zone designation of 4a. Sometimes also called the planting or hardiness zone, this zone number gives you an idea of what plants can and cannot grow in Boulder's climate based on the average extreme annual temperature.Our data is based on the latest 2023 USDA maps, which used Boulder's weather data from 1991 - 2020 in their analysis.
Latest WY growing zone mapIf you are looking for plants suitable for growing in the Boulder area, head on over to our page on plants that grow well in Boulder, WY.
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Latest WY growing zone mapThe growing zone is a measure of the lowest temperature that a plant can survive based on average lowest year temperatures, helping you to decide what plants would grow best in your particular climate. Since Boulder is in growing zone 4a this means that plants there can survive temperatures as low as -30 to -25 degrees Fahrenheit. Plants for Boulder's climate should be chosen with this in mind, or plants should be moved inside to keep their core temperature in the right range if necessary.
Some zones may have been changed by the USDA as of 2023. To see if the Boulder area has been affected, refer to this map of half zone changes from the 2012 version of the USDA zones to the 2023 version.
Half zone changes from 2012 to 2023The updated map shows that over half of the Southeast has warmed by about half a zone. For gardeners, that means you can now grow plants that tolerate a bit more heat and less frost than before. The tan areas reflect this shift. Meanwhile, the white areas had slight temperature changes, but not enough to move them into a new zone. In the Western U.S., a few spots shifted cooler. That’s not due to a colder climate, but because the new map uses a larger dataset, giving a more accurate picture of local conditions. It's important to keep track of these changes when planning your garden!
Hardiness Zone FAQ
Have questions about hardiness zones and what they mean for your garden? Check out our FAQ below for quick answers to common questions about USDA hardiness zones and how they affect plant selection in Boulder, WY.
The USDA hardiness zone is 4a for Boulder. This is sometimes also referred to as the growing or planting zone. These terms are used interchangeably.
Boulder's Growing Zone Details
USDA Growing Zone: 4a
Zip Codes: 82923
Longitude: -109.7067
Latitude: 42.7461
Lowest Avg Temperatures (F): -30 to -25
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Plants For Other States
Looking for the best plants in a different area of the United States? Click on a button below to find plants that are ideal for that state's temperatures.
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