USDA zone 5b in Utah
USDA plant hardiness zone 5b covers 20 locations across Utah (average annual extreme minimum −15 to −10 °F): Antimony, UT, Bluebell, UT, Circleville, UT, Dutch John, UT, Fairview, UT, Fort Duchesne, UT, and 14 more. Average last spring frost across this group ranges May 2 (Randlett) to June 17 (Antimony), and growing seasons run 85–152 days (Antimony to Randlett) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Utah location's own frost dates; the printable planting calendar uses Fort Duchesne, this group's median-season location.
- USDA zone
- 5b−15 to −10 °F
- Last frost range
- May 2–Jun 17avg, 32°F
- First frost range
- Sep 12–Oct 6avg, 32°F
- Growing season range
- 85–152days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Antimony | Kingston, Koosharem | Angle | Jun 17 | Sep 12 | 85 |
| Bluebell | Altamont | Altamont | May 31 | Sep 23 | 112 |
| Circleville | — | Circleville | May 23 | Sep 27 | 125 |
| Dutch John | — | Flaming Gorge | May 26 | Sep 23 | 120 |
| Fairview | — | Scofield-skyline Mine | Jun 13 | Sep 17 | 94 |
| Fort Duchesne * | — | Roosevelt Radio | May 23 | Sep 22 | 121 |
| Garden | — | Lifton Pumping Stn | May 19 | Sep 21 | 123 |
| Hoytsville | — | Coalville | Jun 7 | Sep 12 | 95 |
| Jensen | — | Jensen | May 20 | Sep 25 | 126 |
| Laketown | — | Laketown | May 28 | Sep 24 | 119 |
| Mount Pleasant | Fountain Green, Moroni, Wales | Moroni | May 26 | Sep 25 | 119 |
| Myton | — | Myton | May 7 | Oct 5 | 149 |
| Newcastle | Modena | Enterprise Beryl Jct | May 31 | Sep 20 | 110 |
| Oakley | Samak | Kamas | Jun 5 | Sep 17 | 100 |
| Randlett | — | Ouray 4ne | May 2 | Oct 3 | 152 |
| Roosevelt | Lapoint | Neola | May 19 | Sep 29 | 130 |
| Scipio | — | Scipio | May 22 | Sep 25 | 122 |
| Silver Summit | Peoa | Wanship Dam | Jun 11 | Sep 12 | 92 |
| Trenton | — | Trenton | May 17 | Sep 18 | 121 |
| Vernal | — | Vernal | May 7 | Oct 6 | 150 |
* Fort Duchesne is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Fort Duchesne, representative)
Computed from Fort Duchesne's average frost dates — the median-season location in this Utahzone 5b group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Mar 28 – Apr 11 | May 30 – Jun 6 | Jul 29 – Aug 18 | — | matures comfortably |
| Pepper | Very tender | Mar 14 – Mar 28 | Jun 6 – Jun 13 | Aug 5 – Sep 4 | — | matures comfortably |
| Cucumber | Tender | Apr 25 – May 2 | May 30 – Jun 6 | Jul 19 – Aug 8 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | May 30 – Jun 6 | Jul 14 – Jul 29 | — | matures comfortably |
| Bush bean | Tender | — | May 30 – Jun 6 | Jul 19 – Jul 29 | Jul 24 – Aug 3 | matures comfortably |
| Sweet corn | Tender | — | May 23 – Jun 6 | Jul 22 – Aug 21 | — | matures comfortably |
| Basil | Very tender | Apr 11 – Apr 25 | May 30 – Jun 6 | Jun 29 – Jul 14 | — | matures comfortably |
| Lettuce | Half-hardy | Apr 11 – Apr 25 | Apr 25 – May 9 | Jun 9 – Jun 24 | Jul 10 – Jul 25 | matures comfortably |
| Pea | Hardy | — | Apr 11 – Apr 25 | Jun 5 – Jun 20 | Jun 30 – Jul 15 | matures comfortably |
| Spinach | Hardy | — | Apr 11 – Apr 25 | May 21 – May 31 | Jul 20 – Jul 30 | matures comfortably |
| Carrot | Half-hardy | — | May 2 – May 9 | Jul 1 – Jul 21 | Jun 20 – Jul 10 | matures comfortably |
| Broccoli | Half-hardy | Mar 28 – Apr 11 | Apr 25 – May 9 | Jun 19 – Jul 9 | Jun 25 – Jul 15 | matures comfortably |
Which crops fit this growing season
Using Fort Duchesne's own 121-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Fort Duchesne)
From NOAA's 1991–2020 Climate Normals at station USC00427395. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Jun 8 | Jun 27 | Sep 12 | Sep 25 | 94 |
| 32°F (freeze) | May 23 | Jun 9 | Sep 22 | Oct 3 | 121 |
| 28°F | May 8 | May 25 | Oct 2 | Oct 15 | 145 |
| 24°F | Apr 28 | May 11 | Oct 13 | Oct 27 | 168 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 20 locations is 2,101; Fort Duchesne's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 2,465 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,462 | cool-season crops (brassicas, greens) |
Hardiness zone 5b in Utah
Zone 5b means an average annual extreme minimum winter temperature of about −15 to −10 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Utah spans 9 hardiness zones in this dataset — see all Utah locations for the full range, including zones4a, 5a, 6a, 6b, 7a, 7b, 8a, 8b.
Explore zone 5b in other states at zone 5b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 5b mean in Utah?
- Zone 5b means an average annual extreme minimum winter temperature of −15 to −10 °F — the standard USDA measure of which perennials survive winter. 20 locations in Utah fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in Utah's zone 5b is the growing season longest?
- Randlett runs the longest season on this page at about 152 days; Antimony is shortest at about 85 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in Utah's zone 5b?
- Using Fort Duchesne's frost dates (this page's median-season location): start seeds indoors about Mar 28 – Apr 11, then transplant outside about May 30 – Jun 6. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in Utah's zone 5b have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 20 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.