Frost dates for 84308Cornish, UT
The average last spring frost in Cornish is May 17 and the average first fall frost is September 18, giving a typical growing season of about 121 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 17
- Average first fall frost
- Sep 18
- Growing season
- 121 days
Safer after Jun 6 (1-in-10 risk)
Possible by Sep 1 (1-in-10 risk)
Last frost typically in 203 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 21 · Jun 5 · Jun 21 | Aug 23 · Sep 6 · Sep 21 | 91 days | 100% |
| Frost / freeze (32°F) | May 3 · May 17 · Jun 6 | Sep 1 · Sep 18 · Oct 4 | 121 days | 100% |
| Hard freeze (28°F) | Apr 19 · May 2 · May 17 | Sep 15 · Oct 1 · Oct 16 | 149 days | 100% |
Planting calendar for Cornish
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 16 – Jun 22 |
| Tomatoes | Transplant outdoors | Jun 2 – May 29 |
| Peppers | Start seeds indoors | Apr 16 – May 17 |
| Peppers | Transplant outdoors | Jun 16 – Jul 17 |
| Eggplant | Start seeds indoors | May 3 – Jun 1 |
| Eggplant | Transplant outdoors | Jun 16 – Jul 17 |
| Cucumbers | Sow outdoors | Jun 16 – Jun 8 |
| Summer squash | Sow outdoors | Jun 2 – Jul 17 |
| Winter squash & pumpkins | Sow outdoors | Jun 16 – Jul 17 |
| Snap beans | Sow outdoors | Jun 2 – Jul 1 |
| Sweet corn | Sow outdoors | Jun 2 – May 29 |
| Watermelon & cantaloupe | Sow outdoors | Jun 16 – Jul 17 |
| Okra | Sow outdoors | Jun 9 – Jul 2 |
| Peas | Sow outdoors (spring) | Apr 16 – Jun 1 |
| Potatoes | Plant outdoors (spring) | Apr 16 – Jun 16 |
| Onions | Start seeds indoors (spring) | Mar 5 – Apr 1 |
| Onions | Transplant outdoors (spring) | May 3 – Jun 1 |
| Broccoli | Start seeds indoors (spring) | Mar 29 – May 2 |
| Broccoli | Transplant outdoors (spring) | May 3 – Jun 1 |
| Broccoli | Start seeds indoors (fall) | May 19 – May 29 |
| Broccoli | Transplant outdoors (fall) | Jun 18 – Jun 29 |
| Cabbage | Start seeds indoors (spring) | Mar 19 – Apr 16 |
| Cabbage | Transplant outdoors (spring) | Apr 16 – May 17 |
| Cabbage | Start seeds indoors (fall) | May 9 – Jun 8 |
| Cabbage | Transplant outdoors (fall) | Jun 8 – Jul 9 |
| Leaf lettuce | Sow outdoors (spring) | Apr 16 – Jul 2 |
| Leaf lettuce | Sow outdoors (fall) | Jun 8 – Jul 25 |
| Spinach | Sow outdoors (spring) | Apr 9 – May 23 |
| Spinach | Sow outdoors (fall) | Jun 25 – Jul 30 |
| Radishes | Sow outdoors (spring) | Apr 16 – Jun 6 |
| Radishes | Sow outdoors (fall) | Jun 8 – Aug 9 |
| Kale | Sow outdoors (spring) | May 3 – May 23 |
| Kale | Sow outdoors (fall) | Jun 1 – Jul 9 |
| Carrots | Sow outdoors (spring) | May 17 – Jul 2 |
| Carrots | Sow outdoors (fall) | May 9 – Jun 24 |
| Garlic | Plant outdoors (fall) | Sep 8 – Oct 9 |
Where these dates come from
ZIP code 84308 is matched to the NOAA station Trenton, UT, 6 km away, at 4,455 ft elevation (109 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Trenton, UT (used) | 4,455 ft | May 17 | Sep 18 |
| Richmond, UT | 4,680 ft | May 11 | Oct 5 |
| Cutler Dam, UT | 4,290 ft | May 3 | Oct 12 |
| Preston, ID | 4,719 ft | May 16 | Sep 28 |
Frost dates near Cornish
- Trenton, UT 84338 · last May 17, first Sep 18
- Clarkston, UT 84305 · last May 11, first Oct 5
- Lewiston, UT 84320 · last May 17, first Sep 18
- Newton, UT 84327 · last May 17, first Sep 18
- Weston, ID 83286 · last May 16, first Sep 28
- Richmond, UT 84333 · last May 11, first Oct 5
- Cache Junction, UT 84304 · last May 8, first Oct 2
- Smithfield, UT 84335 · last May 8, first Oct 2
Frequently asked questions
- When is the last frost in Cornish, UT?
- For ZIP code 84308, the average last spring frost (32°F) is May 17, based on NOAA 1991-2020 climate normals for the Trenton, UT weather station. There is a 1-in-10 chance of a frost after June 6.
- When is the first frost in Cornish, UT?
- The average first fall frost (32°F) is September 18. There is a 1-in-10 chance of frost by September 1, so tender plants are at risk from that point on.
- How long is the growing season in 84308?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 121 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.