Smithfield, UT planting zone & frost dates
Smithfield is in USDA hardiness zone 6a. The last spring frost usually comes around May 8 and the first fall frost around October 2, for a growing season of about 144 days.
Planting calendar for Smithfield
Dates are counted from the average last spring frost (May 8) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Mar 13 – Mar 27 Transplant outdoors: May 15 – May 22 |
| Peppers | Start seeds indoors: Feb 27 – Mar 13 Transplant outdoors: May 22 – May 29 |
| Eggplant | Start seeds indoors: Feb 27 – Mar 13 Transplant outdoors: May 22 – May 29 |
| Broccoli | Start seeds indoors: Feb 27 – Mar 13 Transplant outdoors: Apr 10 – Apr 24 |
| Cabbage | Start seeds indoors: Feb 27 – Mar 13 Transplant outdoors: Apr 10 – Apr 24 |
| Onions (sets) | Plant outdoors: Apr 10 – Apr 24 |
| Peas | Sow outdoors: Mar 27 – Apr 10 |
| Spinach | Sow outdoors: Mar 27 – Apr 10 |
| Lettuce | Sow outdoors: Apr 10 – Apr 24 |
| Carrots | Sow outdoors: Apr 10 – Apr 24 |
| Potatoes | Plant outdoors: Apr 10 – Apr 24 |
| Beans | Sow outdoors: May 15 – May 22 |
| Sweet corn | Sow outdoors: May 15 – May 22 |
| Cucumbers | Sow outdoors: May 15 – May 22 |
| Squash & zucchini | Sow outdoors: May 15 – May 22 |
| Basil | Start seeds indoors: Mar 27 – Apr 10 Transplant outdoors: May 15 – May 22 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 7 (8 weeks before the average first fall frost on Oct 2).
Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 24 | May 8 | May 29 |
| First 32°F frost in fall is before | Oct 15 | Oct 2 | Sep 19 |
How to read it: in spring there is a 10% chance of a frost after May 29, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 19. A hard freeze (28°F) usually ends around April 22.
Hardiness zone by ZIP code in Smithfield
- 84335 zone 6a
Nearby cities
- North Logan zone 6a, last frost Apr 30
- Logan zone 6a, last frost May 8
- Brigham City zone 6a, last frost May 5
- North Ogden zone 6b, last frost Apr 19
- Ogden zone 7a, last frost Apr 21
- South Ogden zone 6b, last frost Apr 22
- West Haven zone 7a, last frost Apr 22
- Roy zone 7a, last frost Apr 22
Questions
What growing zone is Smithfield, UT?
Smithfield is in USDA Plant Hardiness Zone 6a (average extreme winter low -10°F to -5°F), according to the USDA 2023 map.
When is the last frost in Smithfield?
The average last spring frost (32°F) in Smithfield is May 8. There is still a 10% chance of frost until May 29.
When can I plant tomatoes in Smithfield?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 15 – May 22. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Logan Cache Ap, UT (USW00094128), 5.9 km (3.7 mi) from the city center, elevation 1358 m, based on 21 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.