USDA Hardiness Zone 9a
Frost Dates for 85730 — Tucson, Arizona
NOAA 1991–2020 normals from Saguaro Np, AZ (3,080 ft), 4 miles east.
Updated
In Tucson, the last spring frost (32°F) is around January 26 in half of years and has passed by February 25 in nine years out of ten. The first fall frost comes around December 16, as early as November 26 one year in ten, leaving a typical freeze-free season of 326 days (NOAA, Saguaro Np, AZ).
- Last spring frost
- January 26
- First fall frost
- December 16
- Growing season
- 326 days
- Hardiness zone
- 9a
50% probability
50% probability
freeze-free, 50%
20 to 25°F (-6.7 to -3.9°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 7%
- Snow per year
- 0.1"
median, 1991–2020
median, 1991–2020
1 of 15 observed
NOAA normal
Frost risk by date in Tucson
Half of springs at Saguaro Np, AZ see their last 32°F night by January 26; only one in ten is past it by December 24, and one in ten still has one after February 25. Planting tender crops after February 6 leaves a 30% risk of a frost on them, after February 14 20%, and after February 25 10%. The 30 days between the even-odds date and the one-in-ten date is wider than at 83% 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 16 in half of years, as early as November 26 one year in ten, and holds off past January 17 one year in ten. A hard freeze of 28°F follows 12 days later, around December 28; in spring the one-in-ten date for 28°F is February 9, 16 days before the 32°F one. The freeze-free season lasts 326 days in a typical year, longer than at 84% of the 98 Arizona stations; it reaches 359 days one year in ten and falls short of 291 one year in ten. On average 8 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 27 days longer, to about February 22, and return around December 2. A 24°F night is unusual: 12% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jan 22 | Feb 2 | Feb 9 | Feb 15 | Feb 22 | Feb 28 | Mar 4 | Mar 8 | Mar 18 |
| 32°F93% of yrs | Dec 24 | Jan 1 | Jan 9 | Jan 17 | Jan 26 | Feb 2 | Feb 6 | Feb 14 | Feb 25 |
| 28°F55% of yrs | Dec 14 | Dec 22 | Dec 29 | Jan 1 | Jan 7 | Jan 13 | Jan 25 | Feb 3 | Feb 9 |
| 24°F12% of yrs | too rare for a date | ||||||||
| 20°F2% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 16 | Nov 21 | Nov 25 | Nov 29 | Dec 2 | Dec 5 | Dec 8 | Dec 12 | Dec 18 |
| 32°F93% of yrs | Nov 26 | Dec 3 | Dec 8 | Dec 12 | Dec 16 | Dec 20 | Dec 24 | Jan 1 | Jan 17 |
| 28°F55% of yrs | Dec 9 | Dec 14 | Dec 19 | Dec 24 | Dec 28 | Jan 2 | Jan 10 | Jan 21 | Feb 3 |
| 24°F12% of yrs | too rare for a date | ||||||||
| 20°F2% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Saguaro Np, 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 85730 →Compare Tucson with another place →
Compared with the next station
The nearest other station, Tucson WFO, AZ, 9 miles west of Tucson and 645 feet lower, has a last frost 6 days earlier (January 20), a first frost 1 day later (December 17), a season 6 days longer.
When it snows in Tucson, Arizona
Measurable snow is rare here: only 1 of 15 winters from 1991 to 2020 recorded 0.1 inch or more at Vail 7 N, AZ, 6.2 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 85730
| When | What to do |
|---|---|
| November 17 – December 1 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 1 – December 15 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| December 29 – January 12 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| January 26 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 23 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by December 2 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 16 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 85730 is 4 miles from Saguaro Np, AZ, which stands at 3,080 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 85710 (Tucson). The 2023 USDA Plant Hardiness Zone Map lists ZIP 85730 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°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.