Frost dates for 81321Cortez, CO
The average last spring frost in Cortez is May 12 and the average first fall frost is October 7, giving a typical growing season of about 147 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 12
- Average first fall frost
- Oct 7
- Growing season
- 147 days
Safer after May 31 (1-in-10 risk)
Possible by Sep 26 (1-in-10 risk)
Last frost typically in 197 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 13 · May 26 · Jun 12 | Sep 18 · Sep 30 · Oct 12 | 125 days | 100% |
| Frost / freeze (32°F) | Apr 30 · May 12 · May 31 | Sep 26 · Oct 7 · Oct 21 | 147 days | 100% |
| Hard freeze (28°F) | Apr 14 · Apr 30 · May 14 | Oct 4 · Oct 17 · Nov 1 | 171 days | 100% |
Planting calendar for Cortez
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 11 – Jun 17 |
| Tomatoes | Transplant outdoors | May 28 – Jun 17 |
| Peppers | Start seeds indoors | Apr 11 – May 12 |
| Peppers | Transplant outdoors | Jun 11 – Jul 12 |
| Eggplant | Start seeds indoors | Apr 28 – May 27 |
| Eggplant | Transplant outdoors | Jun 11 – Jul 12 |
| Cucumbers | Sow outdoors | Jun 11 – Jun 27 |
| Summer squash | Sow outdoors | May 28 – Jul 12 |
| Winter squash & pumpkins | Sow outdoors | Jun 11 – Jul 12 |
| Snap beans | Sow outdoors | May 28 – Jul 20 |
| Sweet corn | Sow outdoors | May 28 – Jun 17 |
| Watermelon & cantaloupe | Sow outdoors | Jun 11 – Jul 12 |
| Okra | Sow outdoors | Jun 4 – Jun 27 |
| Peas | Sow outdoors (spring) | Apr 11 – May 27 |
| Potatoes | Plant outdoors (spring) | Apr 11 – Jun 11 |
| Onions | Start seeds indoors (spring) | Feb 28 – Mar 27 |
| Onions | Transplant outdoors (spring) | Apr 28 – May 27 |
| Broccoli | Start seeds indoors (spring) | Mar 24 – Apr 27 |
| Broccoli | Transplant outdoors (spring) | Apr 28 – May 27 |
| Broccoli | Start seeds indoors (fall) | Jun 7 – Jun 17 |
| Broccoli | Transplant outdoors (fall) | Jul 7 – Jul 18 |
| Cabbage | Start seeds indoors (spring) | Mar 14 – Apr 11 |
| Cabbage | Transplant outdoors (spring) | Apr 11 – May 12 |
| Cabbage | Start seeds indoors (fall) | May 28 – Jun 27 |
| Cabbage | Transplant outdoors (fall) | Jun 27 – Jul 28 |
| Leaf lettuce | Sow outdoors (spring) | Apr 11 – Jun 27 |
| Leaf lettuce | Sow outdoors (fall) | Jun 27 – Aug 13 |
| Spinach | Sow outdoors (spring) | Apr 4 – May 18 |
| Spinach | Sow outdoors (fall) | Jul 14 – Aug 18 |
| Radishes | Sow outdoors (spring) | Apr 11 – Jun 1 |
| Radishes | Sow outdoors (fall) | Jun 27 – Aug 28 |
| Kale | Sow outdoors (spring) | Apr 28 – May 18 |
| Kale | Sow outdoors (fall) | Jun 20 – Jul 28 |
| Carrots | Sow outdoors (spring) | May 12 – Jun 27 |
| Carrots | Sow outdoors (fall) | May 28 – Jul 13 |
| Garlic | Plant outdoors (fall) | Sep 27 – Oct 28 |
Where these dates come from
ZIP code 81321 is matched to the NOAA station Cortez, CO, 1.5 km away, at 6,167 ft elevation (1 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Cortez, CO (used) | 6,167 ft | May 12 | Oct 7 |
| Cortez Montezuma Co Ap, CO | 5,914 ft | May 27 | Sep 28 |
| Cortez 8 Se, CO | 8,035 ft | May 6 | Oct 14 |
| Mesa Verde Np, CO | 7,142 ft | May 9 | Oct 14 |
Frost dates near Cortez
- Dolores, CO 81323 · last May 9, first Oct 14
- Mesa Verde National Park, CO 81330 · last May 9, first Oct 14
- Lewis, CO 81327 · last May 17, first Oct 9
- Towaoc, CO 81334 · last May 27, first Sep 28
- Yellow Jacket, CO 81335 · last May 17, first Oct 9
- Mancos, CO 81328 · last Jun 4, first Sep 24
- Pleasant View, CO 81331 · last May 17, first Oct 9
- Cahone, CO 81320 · last May 17, first Oct 9
Frequently asked questions
- When is the last frost in Cortez, CO?
- For ZIP code 81321, the average last spring frost (32°F) is May 12, based on NOAA 1991-2020 climate normals for the Cortez, CO weather station. There is a 1-in-10 chance of a frost after May 31.
- When is the first frost in Cortez, CO?
- The average first fall frost (32°F) is October 7. There is a 1-in-10 chance of frost by September 26, so tender plants are at risk from that point on.
- How long is the growing season in 81321?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 147 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.