USDA zone 8b in Utah
USDA plant hardiness zone 8b covers 2 locations across Utah (average annual extreme minimum 15 to 20 °F): Apple Valley, UT, St. George, UT. Average last spring frost across this group ranges March 14 (St. George) to April 1 (Apple Valley), and growing seasons run 217–239 days (Apple Valley to St. George) — 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 St. George, this group's median-season location.
- USDA zone
- 8b15 to 20 °F
- Last frost range
- Mar 14–Apr 1avg, 32°F
- First frost range
- Nov 5–Nov 10avg, 32°F
- Growing season range
- 217–239days
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) |
|---|---|---|---|---|---|
| Apple Valley | Toquerville, Leeds | La Verkin | Apr 1 | Nov 5 | 217 |
| St. George * | Washington, Littlefield, Ivins, Santa Clara | St George | Mar 14 | Nov 10 | 239 |
* St. George 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 (St. George, representative)
Computed from St. George's average frost dates — the median-season location in this Utahzone 8b 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 | Jan 17 – Jan 31 | Mar 21 – Mar 28 | May 20 – Jun 9 | — | matures comfortably |
| Pepper | Very tender | Jan 3 – Jan 17 | Mar 28 – Apr 4 | May 27 – Jun 26 | — | matures comfortably |
| Cucumber | Tender | Feb 14 – Feb 21 | Mar 21 – Mar 28 | May 10 – May 30 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Mar 21 – Mar 28 | May 5 – May 20 | — | matures comfortably |
| Bush bean | Tender | — | Mar 21 – Mar 28 | May 10 – May 20 | Sep 11 – Sep 21 | matures comfortably |
| Sweet corn | Tender | — | Mar 14 – Mar 28 | May 13 – Jun 12 | — | matures comfortably |
| Basil | Very tender | Jan 31 – Feb 14 | Mar 21 – Mar 28 | Apr 20 – May 5 | — | matures comfortably |
| Lettuce | Half-hardy | Jan 31 – Feb 14 | Feb 14 – Feb 28 | Mar 31 – Apr 15 | Aug 28 – Sep 12 | matures comfortably |
| Pea | Hardy | — | Jan 31 – Feb 14 | Mar 27 – Apr 11 | Aug 18 – Sep 2 | matures comfortably |
| Spinach | Hardy | — | Jan 31 – Feb 14 | Mar 12 – Mar 22 | Sep 7 – Sep 17 | matures comfortably |
| Carrot | Half-hardy | — | Feb 21 – Feb 28 | Apr 22 – May 12 | Aug 8 – Aug 28 | matures comfortably |
| Broccoli | Half-hardy | Jan 17 – Jan 31 | Feb 14 – Feb 28 | Apr 10 – Apr 30 | Aug 13 – Sep 2 | matures comfortably |
Which crops fit this growing season
Using St. George's own 239-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 (St. George)
From NOAA's 1991–2020 Climate Normals at station USC00427516. 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 | Apr 3 | Apr 21 | Nov 1 | Nov 12 | 208 |
| 32°F (freeze) | Mar 14 | Apr 6 | Nov 10 | Nov 22 | 239 |
| 28°F | Feb 27 | Mar 17 | Nov 20 | Dec 3 | 266 |
| 24°F | Feb 9 | Feb 28 | Dec 1 | Dec 18 | 294 |
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 2 locations is 5,249; St. George's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 5,546 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 8,469 | cool-season crops (brassicas, greens) |
Hardiness zone 8b in Utah
Zone 8b means an average annual extreme minimum winter temperature of about 15 to 20 °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, 5b, 6a, 6b, 7a, 7b, 8a.
Explore zone 8b in other states at zone 8b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 8b mean in Utah?
- Zone 8b means an average annual extreme minimum winter temperature of 15 to 20 °F — the standard USDA measure of which perennials survive winter. 2 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 8b is the growing season longest?
- St. George runs the longest season on this page at about 239 days; Apple Valley is shortest at about 217 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 8b?
- Using St. George's frost dates (this page's median-season location): start seeds indoors about Jan 17 – Jan 31, then transplant outside about Mar 21 – Mar 28. 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 8b 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 2 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.