Frost dates for 81611Aspen, CO
The average last spring frost in Aspen is May 31 and the average first fall frost is September 23, giving a typical growing season of about 114 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 31
- Average first fall frost
- Sep 23
- Growing season
- 114 days
Safer after Jun 14 (1-in-10 risk)
Possible by Sep 11 (1-in-10 risk)
Last frost typically in 216 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 31 · Jun 12 · Jun 26 | Sep 1 · Sep 13 · Sep 24 | 90 days | 100% |
| Frost / freeze (32°F) | May 16 · May 31 · Jun 14 | Sep 11 · Sep 23 · Oct 3 | 114 days | 100% |
| Hard freeze (28°F) | Apr 29 · May 13 · Jun 1 | Sep 21 · Oct 2 · Oct 14 | 140 days | 100% |
Planting calendar for Aspen
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 30 – Jul 6 |
| Tomatoes | Transplant outdoors | Jun 16 – Jun 3 |
| Peppers | Start seeds indoors | Apr 30 – May 31 |
| Peppers | Transplant outdoors | Jun 30 – Jul 31 |
| Eggplant | Start seeds indoors | May 17 – Jun 15 |
| Eggplant | Transplant outdoors | Jun 30 – Jul 31 |
| Cucumbers | Sow outdoors | Jun 30 – Jun 13 |
| Summer squash | Sow outdoors | Jun 16 – Jul 31 |
| Winter squash & pumpkins | Sow outdoors | Jun 30 – Jul 31 |
| Snap beans | Sow outdoors | Jun 16 – Jul 6 |
| Sweet corn | Sow outdoors | Jun 16 – Jun 3 |
| Watermelon & cantaloupe | Sow outdoors | Jun 30 – Jul 31 |
| Okra | Sow outdoors | Jun 23 – Jul 16 |
| Peas | Sow outdoors (spring) | Apr 30 – Jun 15 |
| Potatoes | Plant outdoors (spring) | Apr 30 – Jun 30 |
| Onions | Start seeds indoors (spring) | Mar 19 – Apr 15 |
| Onions | Transplant outdoors (spring) | May 17 – Jun 15 |
| Broccoli | Start seeds indoors (spring) | Apr 12 – May 16 |
| Broccoli | Transplant outdoors (spring) | May 17 – Jun 15 |
| Broccoli | Start seeds indoors (fall) | May 24 – Jun 3 |
| Broccoli | Transplant outdoors (fall) | Jun 23 – Jul 4 |
| Cabbage | Start seeds indoors (spring) | Apr 2 – Apr 30 |
| Cabbage | Transplant outdoors (spring) | Apr 30 – May 31 |
| Cabbage | Start seeds indoors (fall) | May 14 – Jun 13 |
| Cabbage | Transplant outdoors (fall) | Jun 13 – Jul 14 |
| Leaf lettuce | Sow outdoors (spring) | Apr 30 – Jul 16 |
| Leaf lettuce | Sow outdoors (fall) | Jun 13 – Jul 30 |
| Spinach | Sow outdoors (spring) | Apr 23 – Jun 6 |
| Spinach | Sow outdoors (fall) | Jun 30 – Aug 4 |
| Radishes | Sow outdoors (spring) | Apr 30 – Jun 20 |
| Radishes | Sow outdoors (fall) | Jun 13 – Aug 14 |
| Kale | Sow outdoors (spring) | May 17 – Jun 6 |
| Kale | Sow outdoors (fall) | Jun 6 – Jul 14 |
| Carrots | Sow outdoors (spring) | May 31 – Jul 16 |
| Carrots | Sow outdoors (fall) | May 14 – Jun 29 |
| Garlic | Plant outdoors (fall) | Sep 13 – Oct 14 |
Where these dates come from
ZIP code 81611 is matched to the NOAA station Aspen Pitkin Co Ap, CO, 5 km away, at 7,721 ft elevation (141 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Aspen Pitkin Co Ap, CO (used) | 7,721 ft | May 31 | Sep 23 |
| Aspen 1Sw, CO | 8,175 ft | Jun 2 | Sep 23 |
| Meredith, CO | 7,826 ft | — | — |
| Crested Butte, CO | 8,868 ft | — | — |
Frost dates near Aspen
- Aspen, CO 81612 · last May 31, first Sep 23
- Snowmass Village, CO 81615 · last Jun 2, first Sep 23
- Woody Creek, CO 81656 · last May 31, first Sep 23
- Snowmass, CO 81654 · last —, first —
- Meredith, CO 81642 · last Jun 2, first Sep 23
- Basalt, CO 81621 · last May 31, first Sep 23
- Carbondale, CO 81623 · last Jun 2, first Sep 23
- Twin Lakes, CO 81251 · last —, first —
Frequently asked questions
- When is the last frost in Aspen, CO?
- For ZIP code 81611, the average last spring frost (32°F) is May 31, based on NOAA 1991-2020 climate normals for the Aspen Pitkin Co Ap, CO weather station. There is a 1-in-10 chance of a frost after June 14.
- When is the first frost in Aspen, CO?
- The average first fall frost (32°F) is September 23. There is a 1-in-10 chance of frost by September 11, so tender plants are at risk from that point on.
- How long is the growing season in 81611?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 114 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.