Frost dates for 84716Boulder, UT
The average last spring frost in Boulder is May 4 and the average first fall frost is October 14, giving a typical growing season of about 160 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 4
- Average first fall frost
- Oct 14
- Growing season
- 160 days
Safer after May 25 (1-in-10 risk)
Possible by Sep 30 (1-in-10 risk)
Last frost typically in 190 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 18 · Jun 6 | Sep 22 · Oct 5 · Oct 18 | 137 days | 100% |
| Frost / freeze (32°F) | Apr 20 · May 4 · May 25 | Sep 30 · Oct 14 · Oct 29 | 160 days | 100% |
| Hard freeze (28°F) | Apr 5 · Apr 23 · May 12 | Oct 7 · Oct 23 · Nov 9 | 182 days | 100% |
Planting calendar for Boulder
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 3 – Jun 9 |
| Tomatoes | Transplant outdoors | May 20 – Jun 24 |
| Peppers | Start seeds indoors | Apr 3 – May 4 |
| Peppers | Transplant outdoors | Jun 3 – Jul 4 |
| Eggplant | Start seeds indoors | Apr 20 – May 19 |
| Eggplant | Transplant outdoors | Jun 3 – Jul 4 |
| Cucumbers | Sow outdoors | Jun 3 – Jul 4 |
| Summer squash | Sow outdoors | May 20 – Jul 4 |
| Winter squash & pumpkins | Sow outdoors | Jun 3 – Jul 4 |
| Snap beans | Sow outdoors | May 20 – Jul 27 |
| Sweet corn | Sow outdoors | May 20 – Jun 24 |
| Watermelon & cantaloupe | Sow outdoors | Jun 3 – Jul 4 |
| Okra | Sow outdoors | May 27 – Jun 19 |
| Peas | Sow outdoors (spring) | Apr 3 – May 19 |
| Potatoes | Plant outdoors (spring) | Apr 3 – Jun 3 |
| Onions | Start seeds indoors (spring) | Feb 20 – Mar 19 |
| Onions | Transplant outdoors (spring) | Apr 20 – May 19 |
| Broccoli | Start seeds indoors (spring) | Mar 16 – Apr 19 |
| Broccoli | Transplant outdoors (spring) | Apr 20 – May 19 |
| Broccoli | Start seeds indoors (fall) | Jun 14 – Jun 24 |
| Broccoli | Transplant outdoors (fall) | Jul 14 – Jul 25 |
| Cabbage | Start seeds indoors (spring) | Mar 6 – Apr 3 |
| Cabbage | Transplant outdoors (spring) | Apr 3 – May 4 |
| Cabbage | Start seeds indoors (fall) | Jun 4 – Jul 4 |
| Cabbage | Transplant outdoors (fall) | Jul 4 – Aug 4 |
| Leaf lettuce | Sow outdoors (spring) | Apr 3 – Jun 19 |
| Leaf lettuce | Sow outdoors (fall) | Jul 4 – Aug 20 |
| Spinach | Sow outdoors (spring) | Mar 27 – May 10 |
| Spinach | Sow outdoors (fall) | Jul 21 – Aug 25 |
| Radishes | Sow outdoors (spring) | Apr 3 – May 24 |
| Radishes | Sow outdoors (fall) | Jul 4 – Sep 4 |
| Kale | Sow outdoors (spring) | Apr 20 – May 10 |
| Kale | Sow outdoors (fall) | Jun 27 – Aug 4 |
| Carrots | Sow outdoors (spring) | May 4 – Jun 19 |
| Carrots | Sow outdoors (fall) | Jun 4 – Jul 20 |
| Garlic | Plant outdoors (fall) | Oct 4 – Nov 4 |
Where these dates come from
ZIP code 84716 is matched to the NOAA station Boulder, UT, 1.4 km away, at 6,650 ft elevation (148 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Boulder, UT (used) | 6,650 ft | May 4 | Oct 14 |
| Escalante, UT | 5,810 ft | May 8 | Oct 10 |
| Capitol Reef Np, UT | 5,500 ft | Apr 18 | Oct 28 |
| Torrey 7 E, UT | 6,204 ft | Apr 22 | Oct 23 |
Frost dates near Boulder
- Escalante, UT 84726 · last May 8, first Oct 10
- Teasdale, UT 84773 · last May 31, first Sep 21
- Torrey, UT 84775 · last May 31, first Sep 21
- Bicknell, UT 84715 · last May 31, first Sep 21
- Antimony, UT 84712 · last Jun 17, first Sep 12
- Lyman, UT 84749 · last May 31, first Sep 21
- Loa, UT 84747 · last May 31, first Sep 21
- Henrieville, UT 84736 · last May 31, first Sep 28
Frequently asked questions
- When is the last frost in Boulder, UT?
- For ZIP code 84716, the average last spring frost (32°F) is May 4, based on NOAA 1991-2020 climate normals for the Boulder, UT weather station. There is a 1-in-10 chance of a frost after May 25.
- When is the first frost in Boulder, UT?
- The average first fall frost (32°F) is October 14. There is a 1-in-10 chance of frost by September 30, so tender plants are at risk from that point on.
- How long is the growing season in 84716?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 160 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.