Frost dates for 80602Brighton, CO
The average last spring frost in Brighton is May 3 and the average first fall frost is October 7, giving a typical growing season of about 155 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 3
- Average first fall frost
- Oct 7
- Growing season
- 155 days
Safer after May 16 (1-in-10 risk)
Possible by Sep 26 (1-in-10 risk)
Last frost typically in 188 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 3 · May 13 · May 27 | Sep 17 · Sep 30 · Oct 10 | 137 days | 100% |
| Frost / freeze (32°F) | Apr 22 · May 3 · May 16 | Sep 26 · Oct 7 · Oct 19 | 155 days | 100% |
| Hard freeze (28°F) | Apr 8 · Apr 23 · May 7 | Oct 4 · Oct 16 · Oct 29 | 174 days | 100% |
Planting calendar for Brighton
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 2 – Jun 8 |
| Tomatoes | Transplant outdoors | May 19 – Jun 17 |
| Peppers | Start seeds indoors | Apr 2 – May 3 |
| Peppers | Transplant outdoors | Jun 2 – Jul 3 |
| Eggplant | Start seeds indoors | Apr 19 – May 18 |
| Eggplant | Transplant outdoors | Jun 2 – Jul 3 |
| Cucumbers | Sow outdoors | Jun 2 – Jun 27 |
| Summer squash | Sow outdoors | May 19 – Jul 3 |
| Winter squash & pumpkins | Sow outdoors | Jun 2 – Jul 3 |
| Snap beans | Sow outdoors | May 19 – Jul 20 |
| Sweet corn | Sow outdoors | May 19 – Jun 17 |
| Watermelon & cantaloupe | Sow outdoors | Jun 2 – Jul 3 |
| Okra | Sow outdoors | May 26 – Jun 18 |
| Peas | Sow outdoors (spring) | Apr 2 – May 18 |
| Potatoes | Plant outdoors (spring) | Apr 2 – Jun 2 |
| Onions | Start seeds indoors (spring) | Feb 19 – Mar 18 |
| Onions | Transplant outdoors (spring) | Apr 19 – May 18 |
| Broccoli | Start seeds indoors (spring) | Mar 15 – Apr 18 |
| Broccoli | Transplant outdoors (spring) | Apr 19 – May 18 |
| Broccoli | Start seeds indoors (fall) | Jun 7 – Jun 17 |
| Broccoli | Transplant outdoors (fall) | Jul 7 – Jul 18 |
| Cabbage | Start seeds indoors (spring) | Mar 5 – Apr 2 |
| Cabbage | Transplant outdoors (spring) | Apr 2 – May 3 |
| Cabbage | Start seeds indoors (fall) | May 28 – Jun 27 |
| Cabbage | Transplant outdoors (fall) | Jun 27 – Jul 28 |
| Leaf lettuce | Sow outdoors (spring) | Apr 2 – Jun 18 |
| Leaf lettuce | Sow outdoors (fall) | Jun 27 – Aug 13 |
| Spinach | Sow outdoors (spring) | Mar 26 – May 9 |
| Spinach | Sow outdoors (fall) | Jul 14 – Aug 18 |
| Radishes | Sow outdoors (spring) | Apr 2 – May 23 |
| Radishes | Sow outdoors (fall) | Jun 27 – Aug 28 |
| Kale | Sow outdoors (spring) | Apr 19 – May 9 |
| Kale | Sow outdoors (fall) | Jun 20 – Jul 28 |
| Carrots | Sow outdoors (spring) | May 3 – Jun 18 |
| Carrots | Sow outdoors (fall) | May 28 – Jul 13 |
| Garlic | Plant outdoors (fall) | Sep 27 – Oct 28 |
Where these dates come from
ZIP code 80602 is matched to the NOAA station Brighton 3 Se, CO, 6.5 km away, at 5,016 ft elevation (181 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Brighton 3 Se, CO (used) | 5,016 ft | May 3 | Oct 7 |
| Northglenn, CO | 5,407 ft | May 2 | Oct 11 |
| Denver-Stapleton, CO | 5,286 ft | May 4 | Oct 8 |
| Denver Intl Ap, CO | 5,414 ft | May 5 | Oct 9 |
Frost dates near Brighton
- Eastlake, CO 80614 · last May 2, first Oct 11
- Denver, CO 80233 · last May 2, first Oct 11
- Henderson, CO 80640 · last May 3, first Oct 7
- Broomfield, CO 80023 · last May 2, first Oct 11
- Brighton, CO 80601 · last May 3, first Oct 7
- Thornton, CO 80241 · last May 2, first Oct 11
- Dupont, CO 80024 · last May 4, first Oct 8
- Dacono, CO 80514 · last May 3, first Oct 7
Frequently asked questions
- When is the last frost in Brighton, CO?
- For ZIP code 80602, the average last spring frost (32°F) is May 3, based on NOAA 1991-2020 climate normals for the Brighton 3 Se, CO weather station. There is a 1-in-10 chance of a frost after May 16.
- When is the first frost in Brighton, 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 80602?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 155 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.