Find Your Last Frost Date

Last spring frost date confusion - People quote different last spring frost dates for the same area depending on their risk tolerance. Last spring frost dates are important to home Gardeners to help them plan when to set out frost-sensitive annual flower, vegetable and even tropical container plants.

• Last Denver frost dates: In Denver the last spring frost date at a 50 percent confidence level is May 2nd with a growing season of 157 days. If you want to be 80 percent statistically confident it's May 12th and 90 percent confident, May 18th. All dates are based on 47 years of data. The latest last frost date was June 2, 1951.
• Last Colorado Springs frost dates: Dates are not very different considering their 6170 feet elevation versus Denver's 5,290 feet. It is May 5th for 50 percent confidence (153 days), May 13th for 80 percent confidence and May 18th for 90 percent confidence based on 25 years of data. Their latest date was June 3, 1951.
• Last Castle Rock frost dates: Gardeners at 6,250 feet Castle Rock can plan on a last frost date of May 23 with a 50 percent degree of confidence. In Fort Collins, it's May 10, Boulder, May 5 and Brighton, May 2.

Place your bet - Once you know your last spring frost date information, you are ready to place your bet for beating the last spring frost and maximizing the growing season. Simply plant out your tender annuals and see what happens!

For more information on Gardening, contact your local Colorado State University Extension office.