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 map

If 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.

Reusable Grow Bags

Breathable fabric grow bags that promote healthy root growth for your vegetables and fruits.

Raised Garden Planter

Elevated planter for easy access and better drainage.

Brass Watering Can

Elegant brass watering can with classic design and durability.

Large Greenhouse Kit

Spacious greenhouse for extending your growing season.

Hoeing Ain't Easy Garden Sign

Fun and decorative garden sign to add personality to your space.

Latest WY growing zone map

The 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 2023

The 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!

Boulder's Growing Zone Details

Brass Watering Can

Elegant brass watering can with classic design and durability.

Cluck Around Sign

Whimsical sign for your chicken coop area.

Deluxe Plastic Watering Can

High-capacity watering can with comfortable grip and precise spout.

Seed Starting Trays

Perfect for starting seeds indoors before transplanting to your garden.

Raised Garden Bed Kit

Easy-to-assemble raised garden bed for better soil control and drainage.

Map of the Boulder Area

All Towns In WY

Hydroponic Garden Grow Kit

Grow fresh herbs and vegetables year-round with this indoor hydroponic garden system.

Raised Garden Planter

Elevated planter for easy access and better drainage.

Seed Starting Trays

Perfect for starting seeds indoors before transplanting to your garden.

Reusable Grow Bags

Breathable fabric grow bags that promote healthy root growth for your vegetables and fruits.

Fiskars Garden Harvest Basket

Sturdy basket for collecting and carrying your garden harvest.

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.

Steel Hori Hori Weeding Knife

Versatile Japanese-style gardening knife for weeding and planting.

Hoeing Ain't Easy Garden Sign

Fun and decorative garden sign to add personality to your space.

Wooden Chicken Coop

Spacious and secure home for your backyard chickens.

Stainless Steel Garden Tool Set

Complete garden tool set with heavy-duty stainless steel tools for all your gardening needs.

Brass Decorative Faucet Handle

Elegant brass handle to enhance your garden faucet.