USDA Hardiness Zone 10a
Frost Dates for 85255 — Scottsdale, Arizona
NOAA 1991–2020 normals from Pinnacle Peak, AZ (2,565 ft), 3 miles northeast.
Updated
In Scottsdale, the last spring frost (32°F) is around January 27 in half of years and has passed by March 5 in nine years out of ten. The first fall frost comes around December 21, as early as November 28 one year in ten, leaving a typical freeze-free season of 330 days (NOAA, Pinnacle Peak, AZ).
- Last spring frost
- January 27
- First fall frost
- December 21
- Growing season
- 330 days
- Hardiness zone
- 10a
50% probability
50% probability
freeze-free, 50%
30 to 35°F (-1.1 to 1.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 17%
- Snow per year
- 0"
median, 1991–2020
median, 1991–2020
4 of 24 observed
NOAA normal
Frost risk by date in Scottsdale
Half of springs at Pinnacle Peak, AZ see their last 32°F night by January 27; only one in ten is past it by December 23, and one in ten still has one after March 5. Planting tender crops after February 13 leaves a 30% risk of a frost on them, after February 21 20%, and after March 5 10%. The 37 days between the even-odds date and the one-in-ten date is wider than at 97% of the 98 Arizona 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 December 21 in half of years, as early as November 28 one year in ten, and holds off past January 24 one year in ten. A hard freeze of 28°F is less common: it came in 45% of winters. The freeze-free season lasts 330 days in a typical year, longer than at 85% of the 98 Arizona stations; it reaches 365 days one year in ten and falls short of 285 one year in ten. On average 4 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 30 days longer, to about February 26, and return around December 7. A 24°F night is unusual: 10% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jan 17 | Feb 2 | Feb 11 | Feb 19 | Feb 26 | Mar 4 | Mar 9 | Mar 17 | Mar 30 |
| 32°F91% of yrs | Dec 23 | Jan 2 | Jan 9 | Jan 16 | Jan 27 | Feb 5 | Feb 13 | Feb 21 | Mar 5 |
| 28°F45% of yrs | too rare for a date | ||||||||
| 24°F10% of yrs | too rare for a date | ||||||||
| 20°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 19 | Nov 25 | Nov 30 | Dec 4 | Dec 7 | Dec 10 | Dec 14 | Dec 17 | Dec 24 |
| 32°F91% of yrs | Nov 28 | Dec 5 | Dec 11 | Dec 16 | Dec 21 | Dec 25 | Dec 31 | Jan 5 | Jan 24 |
| 28°F45% of yrs | too rare for a date | ||||||||
| 24°F10% of yrs | too rare for a date | ||||||||
| 20°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Pinnacle Peak, 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 85255 →Compare Scottsdale with another place →
Weather by month in Scottsdale
July is the warmest month at Pinnacle Peak, AZ, averaging 99°F by day and 76°F at night; December is the coldest at 63°F and 42°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 34% of years and March still brings one in 10% of years.
Warmth for growing adds up to 7,296 growing degree days a year (base 50°F), more than at 63% of the 102 Arizona stations. 39% of them (2,881) have built up by the end of June, and July adds the most, 1,167.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 64 | 43 | 57% | 1 | 140 |
| Feb | 66 | 45 | 34% | 1 | 173 |
| Mar | 72 | 49 | 10% | <1 | 322 |
| Apr | 79 | 54 | 2% | 0 | 485 |
| May | 87 | 62 | 0% | 0 | 747 |
| Jun | 96 | 71 | 0% | 0 | 1014 |
| Jul | 99 | 76 | 0% | 0 | 1167 |
| Aug | 98 | 75 | 0% | 0 | 1132 |
| Sep | 94 | 71 | 0% | 0 | 966 |
| Oct | 83 | 61 | 0% | 0 | 678 |
| Nov | 72 | 50 | 12% | <1 | 344 |
| Dec | 63 | 42 | 62% | 1 | 130 |
Monthly normals 1991–2020 at Pinnacle Peak, AZ (2,565 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, Scottsdale Municipal Airport, AZ, 5 miles south of Scottsdale and 1,092 feet lower, has a last frost 21 days earlier (January 6), a first frost 5 days later (December 26), a season 23 days longer.
When it snows in Scottsdale, Arizona
Measurable snow is rare here: only 4 of 24 winters from 1991 to 2020 recorded 0.1 inch or more at Carefree, AZ, 8.3 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 85255
| When | What to do |
|---|---|
| November 18 – December 2 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 2 – December 16 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| December 30 – January 13 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| January 27 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 28 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by December 7 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 21 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 85255 is 3 miles from Pinnacle Peak, AZ, which stands at 2,565 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85255 in zone 10a, the band where the coldest night of the year averaged 30 to 35°F (-1.1 to 1.7°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.