Fort Collins, CO Frost Dates
Average frost dates, USDA hardiness zone, and growing season length for Fort Collins, Colorado.
Gardening in Fort Collins
Colorado's craft beer capital is also a serious garden city. CSU's agricultural programs, a food-conscious population, and the Cache la Poudre River valley's fertility create a productive growing culture at altitude.
Zone 5b at 5,000 feet — similar challenges to Denver but with slightly more precipitation. Your 148-day growing season is tight. The intensity of the sun at altitude drives rapid growth, and the Poudre River corridor provides fertile valley soil. Hail remains the nemesis of Front Range gardeners everywhere.
CSU's agricultural heritage gives Fort Collins exceptional gardening expertise. The city's craft beer scene has spawned backyard hop-growing. The Larimer County Farmers Market connects FoCo's food-conscious culture with the agricultural Poudre Valley.
What This Means for Fort Collins Gardeners
The average last spring frost in Fort Collins is around May 5, and the average first fall frost arrives around September 30. That gives you approximately 148 frost-free days to work with.
At 148 days, you're working with a compressed but productive window. Choose varieties by their days-to-maturity number — anything under 75 days is safe, 75-90 requires indoor starting, and 90+ is a calculated risk. The tradeoff: your cool, moderate summers are excellent for crops that heat-zone gardeners struggle with. Your lettuce doesn't bolt in June. Your peas produce for weeks longer. Cool-season crops are your superpower.
These dates are based on NOAA 30-year Climate Normal data for the Fort Collins area. Your actual frost dates could shift 2-3 weeks in either direction in any given year. Learn more about our data sources.
What to Grow in Fort Collins
With 148 frost-free days, Fort Collins gardeners need to plan strategically — start warm-season crops indoors and choose short-season varieties. Cool-season crops are your strength, thriving in the moderate temperatures that define your growing window. Recommended starting points: kale, lettuce, peas, carrots, potatoes, radishes, garlic, and short-season tomatoes.
See the full Colorado planting guide for all 40 plants: Colorado Planting Calendar. Or enter your zip code for exact planting dates personalized to Fort Collins.
More About Zone 5B
Fort Collins is in USDA Hardiness Zone 5B, which means average annual extreme minimum temperatures between -15°F to -10°F. View the full Zone 5B planting guide.
See the complete planting calendar for Colorado: Colorado Planting Calendar.
Other Cities in Colorado
Frequently Asked Questions
These dates are based on NOAA's 30-year Climate Normal data for the Fort Collins area. They represent historical averages, not predictions. In any given year, the actual last frost could be 2-3 weeks earlier or later. Microclimates within Fort Collins (urban heat islands, hilltops, low-lying valleys) can also shift your local frost dates by a week or more.
Start everything possible indoors — your 148-day season doesn't leave room for a slow start. Direct sow only the fastest, hardiest crops (radishes, lettuce, peas) 3-4 weeks before last frost (May 5). Choose short-season varieties for warm crops. Enter your zip code for exact dates.