USDA Hardiness Zone 8b
Frost Dates for 84770 — St George, Utah
NOAA 1991–2020 normals from St George, UT (2,857 ft), under a mile west.
Updated
In St George, the last spring frost (32°F) is around March 14 in half of years and has passed by April 6 in nine years out of ten. The first fall frost comes around November 10, as early as October 27 one year in ten, leaving a typical freeze-free season of 239 days (NOAA, St George, UT).
- Last spring frost
- March 14
- First fall frost
- November 10
- Growing season
- 239 days
- Hardiness zone
- 8b
50% probability
50% probability
freeze-free, 50%
15 to 20°F (-9.4 to -6.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 44%
- Snow per year
- 1.2"
median, 1991–2020
median, 1991–2020
12 of 27 observed
NOAA normal
Frost risk by date in St George
Half of springs at St George, UT see their last 32°F night by March 14; only one in ten is past it by February 27, and one in ten still has one after April 6. Planting tender crops after March 25 leaves a 30% risk of a frost on them, after March 31 20%, and after April 6 10%. The 23 days between the even-odds date and the one-in-ten date is wider than at 86% of the 66 Utah stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.
In fall the first 32°F night comes by November 10 in half of years, as early as October 27 one year in ten, and holds off past November 22 one year in ten. A hard freeze of 28°F follows 10 days later, around November 20; in spring the one-in-ten date for 28°F is March 17, 20 days before the 32°F one. The freeze-free season lasts 239 days in a typical year, the longest of the 66 Utah stations; it reaches 260 days one year in ten and falls short of 212 one year in ten. On average 63 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 20 days longer, to about April 3, and return around November 1. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 47%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 17 | Mar 22 | Mar 27 | Mar 31 | Apr 3 | Apr 8 | Apr 11 | Apr 15 | Apr 21 |
| 32°F | Feb 27 | Mar 4 | Mar 8 | Mar 11 | Mar 14 | Mar 19 | Mar 25 | Mar 31 | Apr 6 |
| 28°F | Feb 7 | Feb 15 | Feb 20 | Feb 24 | Feb 27 | Mar 1 | Mar 5 | Mar 10 | Mar 17 |
| 24°F | Jan 18 | Jan 27 | Feb 2 | Feb 6 | Feb 9 | Feb 13 | Feb 18 | Feb 22 | Feb 28 |
| 20°F93% of yrs | Dec 22 | Jan 1 | Jan 6 | Jan 14 | Jan 21 | Jan 28 | Feb 2 | Feb 6 | Feb 13 |
| 16°F47% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 19 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 12 |
| 32°F | Oct 27 | Nov 1 | Nov 5 | Nov 8 | Nov 10 | Nov 12 | Nov 15 | Nov 18 | Nov 22 |
| 28°F | Nov 7 | Nov 13 | Nov 15 | Nov 18 | Nov 20 | Nov 22 | Nov 25 | Nov 29 | Dec 3 |
| 24°F | Nov 18 | Nov 22 | Nov 24 | Nov 28 | Dec 1 | Dec 4 | Dec 8 | Dec 12 | Dec 18 |
| 20°F93% of yrs | Nov 27 | Dec 4 | Dec 8 | Dec 11 | Dec 16 | Dec 20 | Dec 27 | Jan 1 | Jan 13 |
| 16°F47% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at St George, UT, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 84770 →Compare St George with another place →
Weather by month in St George
July is the warmest month at St George, UT, averaging 102°F by day and 72°F at night; December is the coldest at 53°F and 28°F. A freezing night is all but certain in every month from November to February (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 85% of years and April still brings one in 18% of years.
Warmth for growing adds up to 5,546 growing degree days a year (base 50°F), the most of the 66 Utah stations. 37% of them (2,036) have built up by the end of June, and July adds the most, 1,141. Precipitation totals 9.5 inches a year, most in February (1.4") and least in June (0.2"); May to September bring 29% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 54 | 28 | 1.2 | 100% | 20 | 2 |
| Feb | 59 | 32 | 1.4 | 99% | 10 | 24 |
| Mar | 68 | 39 | 1.0 | 85% | 2 | 146 |
| Apr | 75 | 46 | 0.7 | 18% | <1 | 317 |
| May | 85 | 56 | 0.3 | 0% | 0 | 634 |
| Jun | 96 | 65 | 0.2 | 0% | 0 | 913 |
| Jul | 102 | 72 | 0.5 | 0% | 0 | 1141 |
| Aug | 100 | 70 | 1.1 | 0% | 0 | 1088 |
| Sep | 92 | 61 | 0.7 | 0% | 0 | 796 |
| Oct | 79 | 47 | 0.8 | 18% | <1 | 410 |
| Nov | 64 | 35 | 0.7 | 97% | 8 | 73 |
| Dec | 53 | 28 | 0.9 | 100% | 22 | 2 |
Monthly normals 1991–2020 at St George, UT (2,857 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, La Verkin, UT, 19 miles east of St George and 337 feet higher, has a last frost 18 days later (April 1), a first frost 5 days earlier (November 5), a season 22 days shorter.
When it snows in St George, Utah
Measurable snow is rare here: only 12 of 27 winters from 1991 to 2020 recorded 0.1 inch or more at St George, UT, 0.4 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 84770
| When | What to do |
|---|---|
| January 3 – January 17 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 17 – January 31 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 14 – February 28 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 14 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 18 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 27 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 10 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 84770 is under a mile from St George, UT, which stands at 2,857 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 84790 (St George). The 2023 USDA Plant Hardiness Zone Map lists ZIP 84770 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.