Frost dates for 84338Trenton, UT
The average last spring frost in Trenton 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 197 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 Trenton
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 84338 is matched to the NOAA station Trenton, UT, 1.8 km away, at 4,455 ft elevation (7 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 |
| Logan Cache Ap, UT | 4,454 ft | May 8 | Oct 2 |
Frost dates near Trenton
- Cornish, UT 84308 · last May 17, first Sep 18
- Newton, UT 84327 · last May 17, first Sep 18
- Lewiston, UT 84320 · last May 17, first Sep 18
- Clarkston, UT 84305 · last May 11, first Oct 5
- Smithfield, UT 84335 · last May 8, first Oct 2
- Richmond, UT 84333 · last May 11, first Oct 5
- Cache Junction, UT 84304 · last May 8, first Oct 2
- Weston, ID 83286 · last May 16, first Sep 28
Frequently asked questions
- When is the last frost in Trenton, UT?
- For ZIP code 84338, 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 Trenton, 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 84338?
- 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.