🌷 Your Ultimate Garden Calendar!

🍂 First Frost Dates for Longmont, Colorado 80501

The first 36°F frost date is 30% likely to be on Sep 14. (See detailed probabilities below.)

The first 32°F light freeze date is 30% likely to be on Sep 23. (See detailed probabilities below.)

(See also 🌷 Last Spring Frost Dates.)

First frost date probabilities for Longmont, CO are based on historical climate data.

Always check your local forecast for the most up-to-date frost warnings.

Book Recommendations (ads!)

📚 Growing Under Cover: Techniques for a More Productive, Weather-Resistant, Pest-Free Vegetable Garden

📚 Greenhouse Gardening for Beginners: Step By Step Guide To Build A Year-Round Greenhouse And Grow Herbs, Organic Fruits And Vegetables, Plants, Flowers Plans & Ideas for Extending the Growing Season

📚 How to Garden Indoors & Grow Your Own Food Year Round: Ultimate Guide to Vertical, Container, and Hydroponic Gardening (Creative Homeowner) Vegetables, Herbs, DIY Projects, Composting, Lights, & More

📚 The Year-Round Vegetable Gardener: How to Grow Your Own Food 365 Days a Year, No Matter Where You Live

What is a First Frost Date?

The first fall frost signals the end of your local growing season. This date serves as an important deadline for gardeners and farmers. You'll need to complete harvesting before this point. Annuals and other tender plants will die back when frost hits, and perennial plants will enter their dormant phase for winter. Meanwhile, it's time to enjoy a cup of hot cocoa and a cozy sweater—and start planning your spring garden!

How to use the First Frost Date?

Watch your local weather forecasts in early fall to predict the first frost date. Harvest tender crops and protect vulnerable plants before frost arrives. For late-summer plantings, count backward from your area's average first frost date. This ensures your crops have enough time to mature. Keep track of when frost actually occurs in your garden each year. This helps you identify protected spots where the growing season might last longer.

First Frost Date Probabilities

Probability of frost (36°F) on or before...
10% chanceSep 7
20% chanceSep 12
30% chanceSep 14
40% chanceSep 17
50% chanceSep 19
60% chanceSep 22
70% chanceSep 24
80% chanceSep 26
90% chanceSep 30
Probability of light freeze (32°F) on or before...
10% chanceSep 15
20% chanceSep 20
30% chanceSep 23
40% chanceSep 25
50% chanceSep 27
60% chanceSep 30
70% chanceOct 1
80% chanceOct 4
90% chanceOct 7
Probability of moderate freeze (28°F) on or before...
10% chanceSep 22
20% chanceSep 27
30% chanceSep 30
40% chanceOct 2
50% chanceOct 5
60% chanceOct 7
70% chanceOct 10
80% chanceOct 13
90% chanceOct 17
Probability of moderate hard freeze (24°F) on or before...
10% chanceSep 28
20% chanceOct 4
30% chanceOct 8
40% chanceOct 11
50% chanceOct 14
60% chanceOct 17
70% chanceOct 20
80% chanceOct 23
90% chanceOct 27
Probability of hard freeze (20°F) on or before...
10% chanceOct 8
20% chanceOct 15
30% chanceOct 19
40% chanceOct 22
50% chanceOct 25
60% chanceOct 28
70% chanceOct 31
80% chanceNov 2
90% chanceNov 8
Probability of severe hard freeze (16°F) on or before...
10% chanceOct 20
20% chanceOct 25
30% chanceOct 30
40% chanceNov 1
50% chanceNov 4
60% chanceNov 7
70% chanceNov 11
80% chanceNov 14
90% chanceNov 18

Agricultural climatic data from weather station: LONGMONT 2 ESE (USC00055116)

Back to Weather Calendar