Frost dates for 80465Morrison, CO
The average last spring frost in Morrison is May 16 and the average first fall frost is October 1, giving a typical growing season of about 136 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 16
- Average first fall frost
- Oct 1
- Growing season
- 136 days
Safer after Jun 1 (1-in-10 risk)
Possible by Sep 17 (1-in-10 risk)
Last frost typically in 201 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 14 · May 29 · Jun 12 | Sep 10 · Sep 24 · Oct 5 | 116 days | 100% |
| Frost / freeze (32°F) | May 2 · May 16 · Jun 1 | Sep 17 · Oct 1 · Oct 15 | 136 days | 100% |
| Hard freeze (28°F) | Apr 20 · May 5 · May 20 | Sep 27 · Oct 11 · Oct 26 | 157 days | 100% |
Planting calendar for Morrison
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 15 – Jun 21 |
| Tomatoes | Transplant outdoors | Jun 1 – Jun 11 |
| Peppers | Start seeds indoors | Apr 15 – May 16 |
| Peppers | Transplant outdoors | Jun 15 – Jul 16 |
| Eggplant | Start seeds indoors | May 2 – May 31 |
| Eggplant | Transplant outdoors | Jun 15 – Jul 16 |
| Cucumbers | Sow outdoors | Jun 15 – Jun 21 |
| Summer squash | Sow outdoors | Jun 1 – Jul 16 |
| Winter squash & pumpkins | Sow outdoors | Jun 15 – Jul 16 |
| Snap beans | Sow outdoors | Jun 1 – Jul 14 |
| Sweet corn | Sow outdoors | Jun 1 – Jun 11 |
| Watermelon & cantaloupe | Sow outdoors | Jun 15 – Jul 16 |
| Okra | Sow outdoors | Jun 8 – Jul 1 |
| Peas | Sow outdoors (spring) | Apr 15 – May 31 |
| Potatoes | Plant outdoors (spring) | Apr 15 – Jun 15 |
| Onions | Start seeds indoors (spring) | Mar 4 – Mar 31 |
| Onions | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (spring) | Mar 28 – May 1 |
| Broccoli | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (fall) | Jun 1 – Jun 11 |
| Broccoli | Transplant outdoors (fall) | Jul 1 – Jul 12 |
| Cabbage | Start seeds indoors (spring) | Mar 18 – Apr 15 |
| Cabbage | Transplant outdoors (spring) | Apr 15 – May 16 |
| Cabbage | Start seeds indoors (fall) | May 22 – Jun 21 |
| Cabbage | Transplant outdoors (fall) | Jun 21 – Jul 22 |
| Leaf lettuce | Sow outdoors (spring) | Apr 15 – Jul 1 |
| Leaf lettuce | Sow outdoors (fall) | Jun 21 – Aug 7 |
| Spinach | Sow outdoors (spring) | Apr 8 – May 22 |
| Spinach | Sow outdoors (fall) | Jul 8 – Aug 12 |
| Radishes | Sow outdoors (spring) | Apr 15 – Jun 5 |
| Radishes | Sow outdoors (fall) | Jun 21 – Aug 22 |
| Kale | Sow outdoors (spring) | May 2 – May 22 |
| Kale | Sow outdoors (fall) | Jun 14 – Jul 22 |
| Carrots | Sow outdoors (spring) | May 16 – Jul 1 |
| Carrots | Sow outdoors (fall) | May 22 – Jul 7 |
| Garlic | Plant outdoors (fall) | Sep 21 – Oct 22 |
Where these dates come from
ZIP code 80465 is matched to the NOAA station Roxborough Sp, CO, 22.3 km away, at 6,117 ft elevation (51 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Roxborough Sp, CO (used) | 6,117 ft | May 16 | Oct 1 |
| Marston Fltr Plt, CO | 5,610 ft | May 2 | Oct 11 |
| Evergreen, CO | 6,985 ft | May 23 | Sep 22 |
| Kassler, CO | 5,587 ft | May 8 | Oct 3 |
Frost dates near Morrison
- Littleton, CO 80127 · last May 2, first Oct 11
- Indian Hills, CO 80454 · last May 23, first Sep 22
- Idledale, CO 80453 · last May 23, first Sep 22
- Denver, CO 80228 · last May 3, first Oct 14
- Kittredge, CO 80457 · last May 23, first Sep 22
- Golden, CO 80419 · last Jun 16, first Sep 8
- Evergreen, CO 80437 · last Jun 16, first Sep 8
- Englewood, CO 80110 · last Apr 30, first Oct 12
Frequently asked questions
- When is the last frost in Morrison, CO?
- For ZIP code 80465, the average last spring frost (32°F) is May 16, based on NOAA 1991-2020 climate normals for the Roxborough Sp, CO weather station. There is a 1-in-10 chance of a frost after June 1.
- When is the first frost in Morrison, CO?
- The average first fall frost (32°F) is October 1. There is a 1-in-10 chance of frost by September 17, so tender plants are at risk from that point on.
- How long is the growing season in 80465?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 136 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.