Frost dates for 80643Keenesburg, CO
The average last spring frost in Keenesburg is May 2 and the average first fall frost is October 8, giving a typical growing season of about 159 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 2
- Average first fall frost
- Oct 8
- Growing season
- 159 days
Safer after May 14 (1-in-10 risk)
Possible by Sep 26 (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 18 · Sep 30 · Oct 11 | 139 days | 100% |
| Frost / freeze (32°F) | Apr 17 · May 2 · May 14 | Sep 26 · Oct 8 · Oct 21 | 159 days | 100% |
| Hard freeze (28°F) | Apr 5 · Apr 20 · May 5 | Oct 4 · Oct 18 · Nov 1 | 179 days | 100% |
Planting calendar for Keenesburg
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 18 |
| 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 28 |
| Summer squash | Sow outdoors | May 18 – Jul 2 |
| Winter squash & pumpkins | Sow outdoors | Jun 1 – Jul 2 |
| Snap beans | Sow outdoors | May 18 – Jul 21 |
| Sweet corn | Sow outdoors | May 18 – Jun 18 |
| 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 8 – Jun 18 |
| Broccoli | Transplant outdoors (fall) | Jul 8 – Jul 19 |
| Cabbage | Start seeds indoors (spring) | Mar 4 – Apr 1 |
| Cabbage | Transplant outdoors (spring) | Apr 1 – May 2 |
| Cabbage | Start seeds indoors (fall) | May 29 – Jun 28 |
| Cabbage | Transplant outdoors (fall) | Jun 28 – Jul 29 |
| Leaf lettuce | Sow outdoors (spring) | Apr 1 – Jun 17 |
| Leaf lettuce | Sow outdoors (fall) | Jun 28 – Aug 14 |
| Spinach | Sow outdoors (spring) | Mar 25 – May 8 |
| Spinach | Sow outdoors (fall) | Jul 15 – Aug 19 |
| Radishes | Sow outdoors (spring) | Apr 1 – May 22 |
| Radishes | Sow outdoors (fall) | Jun 28 – Aug 29 |
| Kale | Sow outdoors (spring) | Apr 18 – May 8 |
| Kale | Sow outdoors (fall) | Jun 21 – Jul 29 |
| Carrots | Sow outdoors (spring) | May 2 – Jun 17 |
| Carrots | Sow outdoors (fall) | May 29 – Jul 14 |
| Garlic | Plant outdoors (fall) | Sep 28 – Oct 29 |
Where these dates come from
ZIP code 80643 is matched to the NOAA station Greeley Unc, CO, 40.3 km away, at 4,715 ft elevation (95 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Greeley Unc, CO (used) | 4,715 ft | May 2 | Oct 8 |
| Denver Intl Ap, CO | 5,414 ft | May 5 | Oct 9 |
| Brighton 3 Se, CO | 5,016 ft | May 3 | Oct 7 |
| Byers 5 Ene, CO | 5,101 ft | May 13 | Oct 2 |
Frost dates near Keenesburg
- Roggen, CO 80652 · last May 13, first Oct 2
- Hudson, CO 80642 · last May 3, first Oct 7
- Fort Lupton, CO 80621 · last May 3, first Oct 7
- Brighton, CO 80603 · last May 3, first Oct 7
- Platteville, CO 80651 · last May 7, first Oct 5
- Kersey, CO 80644 · last May 2, first Oct 8
- La Salle, CO 80645 · last May 2, first Oct 8
- Wiggins, CO 80654 · last May 6, first Oct 6
Frequently asked questions
- When is the last frost in Keenesburg, CO?
- For ZIP code 80643, the average last spring frost (32°F) is May 2, based on NOAA 1991-2020 climate normals for the Greeley Unc, CO weather station. There is a 1-in-10 chance of a frost after May 14.
- When is the first frost in Keenesburg, CO?
- The average first fall frost (32°F) is October 8. 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 80643?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 159 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.