Frost dates for 81102Alamosa, CO
The average last spring frost in Alamosa is June 7 and the average first fall frost is September 15, giving a typical growing season of about 98 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Jun 7
- Average first fall frost
- Sep 15
- Growing season
- 98 days
Safer after Jun 24 (1-in-10 risk)
Possible by Sep 4 (1-in-10 risk)
Last frost typically in 223 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) | — | — | 72 days | 100% |
| Frost / freeze (32°F) | May 24 · Jun 7 · Jun 24 | Sep 4 · Sep 15 · Sep 26 | 98 days | 100% |
| Hard freeze (28°F) | May 7 · May 23 · Jun 7 | Sep 14 · Sep 25 · Oct 4 | 124 days | 100% |
Planting calendar for Alamosa
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 | May 7 – Jul 13 |
| Tomatoes | Transplant outdoors | Jun 23 – May 26 |
| Peppers | Start seeds indoors | May 7 – Jun 7 |
| Peppers | Transplant outdoors | Jul 7 – Aug 7 |
| Eggplant | Start seeds indoors | May 24 – Jun 22 |
| Eggplant | Transplant outdoors | Jul 7 – Aug 7 |
| Cucumbers | Sow outdoors | Jul 7 – Jun 5 |
| Summer squash | Sow outdoors | Jun 23 – Aug 7 |
| Winter squash & pumpkins | Sow outdoors | Jul 7 – Aug 7 |
| Snap beans | Sow outdoors | Jun 23 – Jun 28 |
| Sweet corn | Sow outdoors | Jun 23 – May 26 |
| Watermelon & cantaloupe | Sow outdoors | Jul 7 – Aug 7 |
| Okra | Sow outdoors | Jun 30 – Jul 23 |
| Peas | Sow outdoors (spring) | May 7 – Jun 22 |
| Potatoes | Plant outdoors (spring) | May 7 – Jul 7 |
| Onions | Start seeds indoors (spring) | Mar 26 – Apr 22 |
| Onions | Transplant outdoors (spring) | May 24 – Jun 22 |
| Broccoli | Start seeds indoors (spring) | Apr 19 – May 23 |
| Broccoli | Transplant outdoors (spring) | May 24 – Jun 22 |
| Broccoli | Start seeds indoors (fall) | May 16 – May 26 |
| Broccoli | Transplant outdoors (fall) | Jun 15 – Jun 26 |
| Cabbage | Start seeds indoors (spring) | Apr 9 – May 7 |
| Cabbage | Transplant outdoors (spring) | May 7 – Jun 7 |
| Cabbage | Start seeds indoors (fall) | May 6 – Jun 5 |
| Cabbage | Transplant outdoors (fall) | Jun 5 – Jul 6 |
| Leaf lettuce | Sow outdoors (spring) | May 7 – Jul 23 |
| Leaf lettuce | Sow outdoors (fall) | Jun 5 – Jul 22 |
| Spinach | Sow outdoors (spring) | Apr 30 – Jun 13 |
| Spinach | Sow outdoors (fall) | Jun 22 – Jul 27 |
| Radishes | Sow outdoors (spring) | May 7 – Jun 27 |
| Radishes | Sow outdoors (fall) | Jun 5 – Aug 6 |
| Kale | Sow outdoors (spring) | May 24 – Jun 13 |
| Kale | Sow outdoors (fall) | May 29 – Jul 6 |
| Carrots | Sow outdoors (spring) | Jun 7 – Jul 23 |
| Carrots | Sow outdoors (fall) | May 6 – Jun 21 |
| Garlic | Plant outdoors (fall) | Sep 5 – Oct 6 |
Where these dates come from
ZIP code 81102 is matched to the NOAA station Alamosa San Luis Ap, CO, 4.5 km away, at 7,534 ft elevation (13 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Alamosa San Luis Ap, CO (used) | 7,534 ft | Jun 7 | Sep 15 |
| Alamosa 1E, CO | 7,540 ft | May 30 | Sep 17 |
| Waverly 1W, CO | 7,603 ft | Jun 6 | Sep 15 |
| Blanca 4 Nw, CO | 7,709 ft | May 25 | Sep 22 |
Frost dates near Alamosa
- Alamosa, CO 81101 · last Jun 7, first Sep 15
- Mosca, CO 81146 · last Jun 7, first Sep 15
- Homelake, CO 81135 · last Jun 11, first Sep 13
- La Jara, CO 81140 · last Jun 6, first Sep 15
- Sanford, CO 81151 · last May 28, first Sep 21
- Monte Vista, CO 81144 · last Jun 11, first Sep 13
- Hooper, CO 81136 · last May 24, first Sep 24
- Capulin, CO 81124 · last May 28, first Sep 21
Frequently asked questions
- When is the last frost in Alamosa, CO?
- For ZIP code 81102, the average last spring frost (32°F) is June 7, based on NOAA 1991-2020 climate normals for the Alamosa San Luis Ap, CO weather station. There is a 1-in-10 chance of a frost after June 24.
- When is the first frost in Alamosa, CO?
- The average first fall frost (32°F) is September 15. There is a 1-in-10 chance of frost by September 4, so tender plants are at risk from that point on.
- How long is the growing season in 81102?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 98 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.