Frost dates for 80523Fort Collins, CO
The average last spring frost in Fort Collins is May 2 and the average first fall frost is October 7, giving a typical growing season of about 157 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 2
- Average first fall frost
- Oct 7
- Growing season
- 157 days
Safer after May 14 (1-in-10 risk)
Possible by Sep 24 (1-in-10 risk)
Last frost typically in 187 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 1 · May 12 · May 26 | Sep 15 · Sep 29 · Oct 11 | 138 days | 100% |
| Frost / freeze (32°F) | Apr 18 · May 2 · May 14 | Sep 24 · Oct 7 · Oct 20 | 157 days | 100% |
| Hard freeze (28°F) | Apr 5 · Apr 20 · May 5 | Oct 2 · Oct 17 · Oct 28 | 179 days | 100% |
Planting calendar for Fort Collins
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 1 – Jun 7 |
| Tomatoes | Transplant outdoors | May 18 – Jun 17 |
| Peppers | Start seeds indoors | Apr 1 – May 2 |
| Peppers | Transplant outdoors | Jun 1 – Jul 2 |
| Eggplant | Start seeds indoors | Apr 18 – May 17 |
| Eggplant | Transplant outdoors | Jun 1 – Jul 2 |
| Cucumbers | Sow outdoors | Jun 1 – Jun 27 |
| Summer squash | Sow outdoors | May 18 – Jul 2 |
| Winter squash & pumpkins | Sow outdoors | Jun 1 – Jul 2 |
| Snap beans | Sow outdoors | May 18 – Jul 20 |
| Sweet corn | Sow outdoors | May 18 – Jun 17 |
| Watermelon & cantaloupe | Sow outdoors | Jun 1 – Jul 2 |
| Okra | Sow outdoors | May 25 – Jun 17 |
| Peas | Sow outdoors (spring) | Apr 1 – May 17 |
| Potatoes | Plant outdoors (spring) | Apr 1 – Jun 1 |
| Onions | Start seeds indoors (spring) | Feb 18 – Mar 17 |
| Onions | Transplant outdoors (spring) | Apr 18 – May 17 |
| Broccoli | Start seeds indoors (spring) | Mar 14 – Apr 17 |
| Broccoli | Transplant outdoors (spring) | Apr 18 – May 17 |
| Broccoli | Start seeds indoors (fall) | Jun 7 – Jun 17 |
| Broccoli | Transplant outdoors (fall) | Jul 7 – Jul 18 |
| Cabbage | Start seeds indoors (spring) | Mar 4 – Apr 1 |
| Cabbage | Transplant outdoors (spring) | Apr 1 – May 2 |
| Cabbage | Start seeds indoors (fall) | May 28 – Jun 27 |
| Cabbage | Transplant outdoors (fall) | Jun 27 – Jul 28 |
| Leaf lettuce | Sow outdoors (spring) | Apr 1 – Jun 17 |
| Leaf lettuce | Sow outdoors (fall) | Jun 27 – Aug 13 |
| Spinach | Sow outdoors (spring) | Mar 25 – May 8 |
| Spinach | Sow outdoors (fall) | Jul 14 – Aug 18 |
| Radishes | Sow outdoors (spring) | Apr 1 – May 22 |
| Radishes | Sow outdoors (fall) | Jun 27 – Aug 28 |
| Kale | Sow outdoors (spring) | Apr 18 – May 8 |
| Kale | Sow outdoors (fall) | Jun 20 – Jul 28 |
| Carrots | Sow outdoors (spring) | May 2 – Jun 17 |
| Carrots | Sow outdoors (fall) | May 28 – Jul 13 |
| Garlic | Plant outdoors (fall) | Sep 27 – Oct 28 |
Where these dates come from
ZIP code 80523 is matched to the NOAA station Ft Collins, CO, 1 km away, at 5,004 ft elevation (1 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Ft Collins, CO (used) | 5,004 ft | May 2 | Oct 7 |
| Ft Collins 4 E, CO | 4,920 ft | May 3 | Oct 6 |
| Loveland 2N, CO | 5,080 ft | May 10 | Oct 1 |
| Buckhorn Mtn 1 E, CO | 7,400 ft | May 21 | Sep 29 |
Frost dates near Fort Collins
- Fort Collins, CO 80527 · last May 2, first Oct 7
- Laporte, CO 80535 · last May 2, first Oct 7
- Timnath, CO 80547 · last May 3, first Oct 6
- Masonville, CO 80541 · last May 12, first Oct 1
- Bellvue, CO 80512 · last May 21, first Sep 29
- Wellington, CO 80549 · last May 2, first Oct 7
- Loveland, CO 80538 · last May 10, first Oct 1
- Windsor, CO 80550 · last May 3, first Oct 6
Frequently asked questions
- When is the last frost in Fort Collins, CO?
- For ZIP code 80523, the average last spring frost (32°F) is May 2, based on NOAA 1991-2020 climate normals for the Ft Collins, CO weather station. There is a 1-in-10 chance of a frost after May 14.
- When is the first frost in Fort Collins, CO?
- The average first fall frost (32°F) is October 7. There is a 1-in-10 chance of frost by September 24, so tender plants are at risk from that point on.
- How long is the growing season in 80523?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 157 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.