USDA Hardiness Zone 8b
Frost Dates for 85650 — Sierra Vista, Arizona
NOAA 1991–2020 normals from Sierra Vista, AZ (4,606 ft), 4 miles northwest.
Updated
In Sierra Vista, the last spring frost (32°F) is around April 5 in half of years and has passed by April 21 in nine years out of ten. The first fall frost comes around November 9, as early as October 23 one year in ten, leaving a typical freeze-free season of 216 days (NOAA, Sierra Vista, AZ).
- Last spring frost
- April 5
- First fall frost
- November 9
- Growing season
- 216 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
- 17%
- Snow per year
- 0.4"
median, 1991–2020
median, 1991–2020
3 of 18 observed
NOAA normal
Frost risk by date in Sierra Vista
Half of springs at Sierra Vista, AZ see their last 32°F night by April 5; only one in ten is past it by March 15, and one in ten still has one after April 21. Planting tender crops after April 11 leaves a 30% risk of a frost on them, after April 15 20%, and after April 21 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 88% of the 98 Arizona stations behind this site's ZIP pages.
In fall the first 32°F night comes by November 9 in half of years, as early as October 23 one year in ten, and holds off past November 23 one year in ten. A hard freeze of 28°F follows 12 days later, around November 21; in spring the one-in-ten date for 28°F is April 5, 16 days before the 32°F one. The freeze-free season lasts 216 days in a typical year, shorter than at 62% of the 98 Arizona stations; it reaches 239 days one year in ten and falls short of 194 one year in ten. On average 45 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 15 days longer, to about April 20, and return around October 30. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 48%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 5 | Apr 9 | Apr 13 | Apr 16 | Apr 20 | Apr 23 | Apr 27 | Apr 30 | May 4 |
| 32°F | Mar 15 | Mar 24 | Mar 30 | Apr 2 | Apr 5 | Apr 8 | Apr 11 | Apr 15 | Apr 21 |
| 28°F | Feb 21 | Feb 28 | Mar 7 | Mar 10 | Mar 15 | Mar 20 | Mar 25 | Mar 31 | Apr 5 |
| 24°F | Jan 20 | Jan 31 | Feb 7 | Feb 14 | Feb 19 | Feb 24 | Mar 1 | Mar 6 | Mar 15 |
| 20°F93% of yrs | Dec 25 | Jan 3 | Jan 9 | Jan 15 | Jan 24 | Jan 31 | Feb 5 | Feb 12 | Feb 20 |
| 16°F48% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 15 | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 12 |
| 32°F | Oct 23 | Oct 29 | Nov 2 | Nov 5 | Nov 9 | Nov 12 | Nov 15 | Nov 18 | Nov 23 |
| 28°F | Nov 4 | Nov 10 | Nov 15 | Nov 18 | Nov 21 | Nov 24 | Nov 27 | Dec 1 | Dec 5 |
| 24°F | Nov 16 | Nov 22 | Nov 26 | Nov 30 | Dec 3 | Dec 6 | Dec 10 | Dec 15 | Dec 21 |
| 20°F93% of yrs | Nov 28 | Dec 4 | Dec 10 | Dec 15 | Dec 20 | Dec 24 | Dec 29 | Jan 4 | Jan 17 |
| 16°F48% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Sierra Vista, AZ, 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 85650 →Compare Sierra Vista with another place →
Weather by month in Sierra Vista
July is the warmest month at Sierra Vista, AZ, averaging 92°F by day and 63°F at night; January is the coldest at 61°F and 30°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 64% of years.
Warmth for growing adds up to 4,768 growing degree days a year (base 50°F), fewer than at 65% of the 102 Arizona stations. 40% of them (1,895) have built up by the end of June, and July adds the most, 837. Precipitation totals 13.0 inches a year, most in July (3.5") and least in May (0.2"); May to September bring 68% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 61 | 30 | 0.8 | 100% | 15 | 22 |
| Feb | 64 | 33 | 0.6 | 100% | 8 | 52 |
| Mar | 71 | 38 | 0.5 | 95% | 3 | 160 |
| Apr | 78 | 43 | 0.3 | 64% | <1 | 309 |
| May | 85 | 50 | 0.2 | 1% | 0 | 549 |
| Jun | 94 | 60 | 0.5 | 0% | 0 | 802 |
| Jul | 92 | 63 | 3.5 | 0% | 0 | 837 |
| Aug | 90 | 62 | 3.3 | 0% | 0 | 790 |
| Sep | 87 | 57 | 1.3 | 0% | 0 | 652 |
| Oct | 80 | 47 | 0.6 | 27% | <1 | 423 |
| Nov | 70 | 37 | 0.5 | 97% | 4 | 147 |
| Dec | 62 | 30 | 0.9 | 100% | 15 | 23 |
Monthly normals 1991–2020 at Sierra Vista, AZ (4,606 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, Coronado Nmem, AZ, 10 miles south of Sierra Vista and 636 feet higher, has a last frost 2 days later (April 7), the same first-frost date, a season 3 days shorter.
When it snows in Sierra Vista, Arizona
Measurable snow is rare here: only 3 of 18 winters from 1991 to 2020 recorded 0.1 inch or more at Sierra Vista, AZ, 3.7 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 85650
| When | What to do |
|---|---|
| January 25 – February 8 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 8 – February 22 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 8 – March 22 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 5 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 17 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 26 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 9 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 85650 is 4 miles from Sierra Vista, AZ, which stands at 4,606 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 85635 (Sierra Vista). The 2023 USDA Plant Hardiness Zone Map lists ZIP 85650 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.