USDA Hardiness Zone 9b
Frost Dates for 85743 — Tucson, Arizona
NOAA 1991–2020 normals from Tucson 17 NW, AZ (2,561 ft), 6 miles southwest.
Updated
In Tucson, the last spring frost (32°F) is around February 23 in half of years and has passed by March 22 in nine years out of ten. The first fall frost comes around December 6, as early as November 18 one year in ten, leaving a typical freeze-free season of 287 days (NOAA, Tucson 17 NW, AZ).
- Last spring frost
- February 23
- First fall frost
- December 6
- Growing season
- 287 days
- Hardiness zone
- 9b
50% probability
50% probability
freeze-free, 50%
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 5%
- Snow per year
- 0"
median, 1991–2020
median, 1991–2020
1 of 19 observed
NOAA normal
Frost risk by date in Tucson
Half of springs at Tucson 17 NW, AZ see their last 32°F night by February 23; only one in ten is past it by January 15, and one in ten still has one after March 22. Planting tender crops after March 5 leaves a 30% risk of a frost on them, after March 11 20%, and after March 22 10%. The 27 days between the even-odds date and the one-in-ten date is wider than at 71% 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 6 in half of years, as early as November 18 one year in ten, and holds off past December 25 one year in ten. A hard freeze of 28°F follows 13 days later, around December 19; in spring the one-in-ten date for 28°F is March 1, 21 days before the 32°F one. The freeze-free season lasts 287 days in a typical year, longer than at 67% of the 98 Arizona stations; it reaches 324 days one year in ten and falls short of 254 one year in ten. On average 11 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 March 15, and return around November 24. A 24°F night is unusual: 38% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Feb 22 | Feb 28 | Mar 6 | Mar 10 | Mar 15 | Mar 20 | Mar 26 | Apr 1 | Apr 10 |
| 32°F | Jan 15 | Jan 31 | Feb 9 | Feb 16 | Feb 23 | Mar 1 | Mar 5 | Mar 11 | Mar 22 |
| 28°F87% of yrs | Dec 19 | Dec 30 | Jan 4 | Jan 11 | Jan 22 | Feb 1 | Feb 7 | Feb 15 | Mar 1 |
| 24°F38% of yrs | too rare for a date | ||||||||
| 20°F7% of yrs | too rare for a date | ||||||||
| 16°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 7 | Nov 13 | Nov 17 | Nov 21 | Nov 24 | Nov 28 | Dec 2 | Dec 5 | Dec 10 |
| 32°F | Nov 18 | Nov 24 | Nov 29 | Dec 3 | Dec 6 | Dec 9 | Dec 12 | Dec 17 | Dec 25 |
| 28°F87% of yrs | Nov 30 | Dec 5 | Dec 10 | Dec 14 | Dec 19 | Dec 24 | Dec 29 | Jan 5 | Jan 22 |
| 24°F38% of yrs | too rare for a date | ||||||||
| 20°F7% of yrs | too rare for a date | ||||||||
| 16°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Tucson 17 NW, 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 85743 →Compare Tucson with another place →
Weather by month in Tucson
July is the warmest month at Tucson 17 NW, AZ, averaging 102°F by day and 74°F at night; December is the coldest at 66°F and 39°F. A freezing night is all but certain in December (a 90% chance or more). From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 63% of years and March still brings one in 38% of years.
Warmth for growing adds up to 7,494 growing degree days a year (base 50°F), more than at 67% of the 102 Arizona stations. 41% of them (3,069) have built up by the end of June, and July adds the most, 1,175. Precipitation totals 11.1 inches a year, most in July (2.1") and least in May (0.2"); May to September bring 53% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 67 | 39 | 1.0 | 87% | 3 | 141 |
| Feb | 70 | 41 | 1.0 | 63% | 2 | 178 |
| Mar | 76 | 46 | 0.7 | 38% | <1 | 348 |
| Apr | 84 | 51 | 0.3 | 5% | <1 | 529 |
| May | 93 | 59 | 0.2 | 0% | 0 | 805 |
| Jun | 102 | 69 | 0.3 | 0% | 0 | 1068 |
| Jul | 102 | 74 | 2.1 | 0% | 0 | 1175 |
| Aug | 100 | 73 | 2.0 | 0% | 0 | 1122 |
| Sep | 97 | 68 | 1.3 | 0% | 0 | 964 |
| Oct | 87 | 57 | 0.7 | 0% | 0 | 687 |
| Nov | 76 | 47 | 0.5 | 34% | 1 | 345 |
| Dec | 66 | 39 | 1.0 | 90% | 5 | 132 |
Monthly normals 1991–2020 at Tucson 17 NW, AZ (2,561 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, Tucson 11 W, AZ, 7 miles south of Tucson and 172 feet higher, has a last frost 15 days earlier (February 8), a first frost 4 days later (December 10), a season 16 days longer.
When it snows in Tucson, Arizona
Measurable snow is rare here: only 1 of 19 winters from 1991 to 2020 recorded 0.1 inch or more at Tucson 17 NW, AZ, 6.2 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 85743
| When | What to do |
|---|---|
| December 15 – December 29 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 29 – January 12 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 26 – February 9 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 23 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 13 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 22 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 6 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 85743 is 6 miles from Tucson 17 NW, AZ, which stands at 2,561 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85743 in zone 9b, the band where the coldest night of the year averaged 25 to 30°F (-3.9 to -1.1°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.