US Grow Zones

St. George, Utah: planting zone & frost dates

Last updated · Sources: PRISM/OSU 2023 ZIP zone listings; NOAA NCEI 1991–2020 Climate Normals (station USC00427516); U.S. Census Bureau — see methodology

St. George is in USDA plant hardiness zone 8b, where the average coldest winter night reaches 15 to 20°F (-9.4 to -6.7°C). The typical last spring frost is around Mar 25 and the first fall frost around Nov 5.

Hardiness zone8B15 to 20°F
Last spring frostMar 2530% chance of frost after
First fall frostNov 530% chance of frost before
Growing season239 daysmedian frost-free days

Frost dates

ProbabilityLast spring frost (32°F)First fall frost (32°F)
Safer (10% risk)Apr 6Oct 27
Typical planning date (30% risk)Mar 25Nov 5
Median (50%)Mar 14Nov 10

How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.

Frost data comes from NOAA station ST GEORGE, UT (USC00427516), 3.4 mi (5.4 km) from the city center and 328 ft higher than the city center (+100 m). Record used for the 1991–2020 normals: 23 years.

Frost probability in spring and fall, St. George, UTChance of a 32°F frost in St. George, UT, NOAA 1991–2020. Spring: the chance of another frost falls from 90% on Feb 27 to 10% on Apr 6. Fall: the chance that the first frost has arrived rises from 10% on Oct 27 to 90% on Nov 22.0%50%100%Spring: later frostFeb 1Mar 1Apr 130%: Mar 25Fall: frost arrivedNov 1Nov 15Dec 130%: Nov 532°F frost28°F hard freezeplanning date
Shaded areas show the chance of a 32°F frost: falling through spring, rising through fall. The dashed line is the 28°F hard-freeze curve. Data: NOAA 1991–2020 Normals, station USC00427516.
Frost-free growing season in St. George, UT1 in 10 risk: Apr 6 to Oct 27 (204 days); 3 in 10 risk: Mar 25 to Nov 5 (225 days); Median (50%): Mar 14 to Nov 10 (241 days); No 28°F freeze: Feb 27 to Nov 20 (266 days). In 9 of 10 years the 32°F-free season is at least 212 days.Frost-free days, spring to fallJFMAMJJASOND1 in 10 risk204 days3 in 10 risk225 daysMedian (50%)241 daysNo 28°F freeze266 days
Frost-free window at three risk levels, plus the window between 28°F hard freezes. Read about what the probabilities mean.

Why your yard may differ from the station: microclimates.

Hardiness zone across St. George

All 3 ZIP codes covering St. George are in zone 8b.

ZIP codes in St. George and their zones
ZIPZoneShare of city land
847908b60.1%
847708b37.7%
847808b1.9%

Vegetable planting calendar for St. George

Dates are counted from the 30%-risk frost dates above (last frost Mar 25, first frost Nov 5). Shift a week later in cold spots or low-lying ground.

CropStart indoorsTransplant / plant outDirect sowFall crop sow/plant
TomatoJan 28 – Feb 11Apr 1 – Apr 15——
PepperJan 14 – Jan 28Apr 8 – Apr 22——
LettuceFeb 11 – Feb 25Mar 11 – Apr 1Feb 25 – Apr 8Aug 27 – Sep 24
Green Beans——Apr 1 – May 6Aug 13 – Aug 27
Sweet Corn——Apr 1 – Apr 29—
Zucchini & Summer SquashFeb 25 – Mar 4Apr 1 – Apr 15Apr 1 – Apr 22Aug 13 – Aug 27
CucumberFeb 25 – Mar 4Apr 8 – Apr 15Apr 1 – Apr 22Aug 13 – Aug 27
Carrot——Mar 4 – Apr 8Aug 13 – Aug 27
OnionDec 31 – Jan 14Feb 25 – Mar 11——
Potato—Feb 25 – Mar 18——
BasilFeb 11 – Feb 25Apr 8 – Apr 22Apr 8 – Apr 29—
Spinach——Feb 11 – Mar 11Sep 10 – Oct 8
KaleJan 28 – Feb 11Feb 25 – Mar 18Feb 25 – Mar 18Aug 27 – Sep 24
BroccoliJan 28 – Feb 11Mar 11 – Apr 1—Aug 13 – Aug 27
Peas——Feb 11 – Mar 4Aug 27 – Sep 10
EggplantJan 14 – Jan 28Apr 8 – Apr 22——
CabbageJan 28 – Feb 11Feb 25 – Mar 11—Aug 13 – Aug 27
Radish——Feb 18 – Apr 8Sep 24 – Oct 22
Strawberry—Feb 25 – Mar 18——
Beets——Mar 4 – Apr 15Aug 27 – Sep 10

Nearby cities in Utah

More: all Utah cities · other zone 8b cities: Dallas, TX, Fort Worth, TX, El Paso, TX, Virginia Beach, VA, Arlington, TX, Plano, TX, Irving, TX, Garland, TX

St. George gardening questions

When is the last frost in St. George, UT?

Plan around Mar 25. At NOAA's St George, UT station, 3.4 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Mar 14, and after Apr 6 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Feb 27. The 90% and 10% dates are 38 days apart, close to the 36-day median for cities on this site.

When should I plant tomatoes in St. George, UT?

Start seeds indoors Jan 28 – Feb 11 and set transplants outside Apr 1 – Apr 15, once nights stay above 50°F and the soil is near 60°F. That leaves 225 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.

How long is the growing season in St. George?

About 239 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 212 days, and in 1 year in 10 it runs 260 days or more. In fall there is a 10% chance of frost by Oct 27 and a 30% chance by Nov 5. That is the longest of the 11 Utah cities on this site.

When should I plant a fall garden in St. George?

Count back from the first fall frost (Nov 5): transplant broccoli Aug 13 – Aug 27; sow kale Aug 27 – Sep 24; sow lettuce Aug 27 – Sep 24; sow radishes Sep 24 – Oct 22. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 20. How the math works: succession and fall planting.

Did St. George's hardiness zone change on the 2023 map?

Yes. Most of St. George was zone 8a on the 2012 map and is zone 8b on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.

How does St. George compare with North Las Vegas, NV?

St. George is zone 8b and North Las Vegas is zone 9b. The typical last spring frost in St. George (Mar 25) comes about 42 days later than in North Las Vegas, NV (Feb 11), 100 miles away, and the first fall frost is Nov 5 versus Dec 1. St. George sits about 419 ft higher, which explains part of the gap. The two cities use different NOAA stations.