USDA zone 8a in Utah
USDA plant hardiness zone 8a covers 6 locations across Utah (average annual extreme minimum 10 to 15 °F): Dammeron Valley, UT, Halls Crossing, UT, La Verkin, UT, Oljato-Monument Valley, UT, Rockville, UT, Veyo, UT. Average last spring frost across this group ranges March 14 (Dammeron Valley) to April 13 (Rockville), and growing seasons run 201–239 days (Oljato-Monument Valley to Dammeron Valley) — 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 La Verkin, this group's median-season location.
- USDA zone
- 8a10 to 15 °F
- Last frost range
- Mar 14–Apr 13avg, 32°F
- First frost range
- Oct 30–Nov 10avg, 32°F
- Growing season range
- 201–239days
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) |
|---|---|---|---|---|---|
| Dammeron Valley | — | St George | Mar 14 | Nov 10 | 239 |
| Halls Crossing | — | Bullfrog Basin | Mar 25 | Nov 10 | 227 |
| La Verkin * | — | La Verkin | Apr 1 | Nov 5 | 217 |
| Oljato-Monument Valley | — | Mexican Hat | Apr 11 | Oct 30 | 201 |
| Rockville | — | Zion Np | Apr 13 | Nov 2 | 202 |
| Veyo | — | Veyo Powerhouse | Apr 9 | Nov 5 | 207 |
* La Verkin 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 (La Verkin, representative)
Computed from La Verkin's average frost dates — the median-season location in this Utahzone 8a 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 | Feb 4 – Feb 18 | Apr 8 – Apr 15 | Jun 7 – Jun 27 | — | matures comfortably |
| Pepper | Very tender | Jan 21 – Feb 4 | Apr 15 – Apr 22 | Jun 14 – Jul 14 | — | matures comfortably |
| Cucumber | Tender | Mar 4 – Mar 11 | Apr 8 – Apr 15 | May 28 – Jun 17 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Apr 8 – Apr 15 | May 23 – Jun 7 | — | matures comfortably |
| Bush bean | Tender | — | Apr 8 – Apr 15 | May 28 – Jun 7 | Sep 6 – Sep 16 | matures comfortably |
| Sweet corn | Tender | — | Apr 1 – Apr 15 | May 31 – Jun 30 | — | matures comfortably |
| Basil | Very tender | Feb 18 – Mar 4 | Apr 8 – Apr 15 | May 8 – May 23 | — | matures comfortably |
| Lettuce | Half-hardy | Feb 18 – Mar 4 | Mar 4 – Mar 18 | Apr 18 – May 3 | Aug 23 – Sep 7 | matures comfortably |
| Pea | Hardy | — | Feb 18 – Mar 4 | Apr 14 – Apr 29 | Aug 13 – Aug 28 | matures comfortably |
| Spinach | Hardy | — | Feb 18 – Mar 4 | Mar 30 – Apr 9 | Sep 2 – Sep 12 | matures comfortably |
| Carrot | Half-hardy | — | Mar 11 – Mar 18 | May 10 – May 30 | Aug 3 – Aug 23 | matures comfortably |
| Broccoli | Half-hardy | Feb 4 – Feb 18 | Mar 4 – Mar 18 | Apr 28 – May 18 | Aug 8 – Aug 28 | matures comfortably |
Which crops fit this growing season
Using La Verkin's own 217-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 (La Verkin)
From NOAA's 1991–2020 Climate Normals at station USC00424968. 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 20 | May 9 | Oct 27 | Nov 8 | 191 |
| 32°F (freeze) | Apr 1 | Apr 24 | Nov 5 | Nov 17 | 217 |
| 28°F | Mar 4 | Apr 2 | Nov 15 | Nov 28 | 254 |
| 24°F | Feb 13 | Mar 5 | Nov 26 | Dec 13 | 286 |
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 6 locations is 4,935; La Verkin's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 4,952 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 7,808 | cool-season crops (brassicas, greens) |
Hardiness zone 8a in Utah
Zone 8a means an average annual extreme minimum winter temperature of about 10 to 15 °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, 8b.
Explore zone 8a in other states at zone 8a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 8a mean in Utah?
- Zone 8a means an average annual extreme minimum winter temperature of 10 to 15 °F — the standard USDA measure of which perennials survive winter. 6 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 8a is the growing season longest?
- Dammeron Valley runs the longest season on this page at about 239 days; Oljato-Monument Valley is shortest at about 201 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 8a?
- Using La Verkin's frost dates (this page's median-season location): start seeds indoors about Feb 4 – Feb 18, then transplant outside about Apr 8 – Apr 15. 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 8a 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 6 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.