USDA Hardiness Zone 9b
Frost Dates for 85742 — Tucson, Arizona
NOAA 1991–2020 normals from Tohono Chul, AZ (2,527 ft), 5 miles southeast.
Updated
In Tucson, the last spring frost (32°F) is around February 26 in half of years and has passed by March 18 in nine years out of ten. The first fall frost comes around December 4, as early as November 17 one year in ten, leaving a typical freeze-free season of 279 days (NOAA, Tohono Chul, AZ).
- Last spring frost
- February 26
- First fall frost
- December 4
- Growing season
- 279 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 22 observed
NOAA normal
Frost risk by date in Tucson
Half of springs at Tohono Chul, AZ see their last 32°F night by February 26; only one in ten is past it by January 29, and one in ten still has one after March 18. Planting tender crops after March 5 leaves a 30% risk of a frost on them, after March 9 20%, and after March 18 10%. The 20 days between the even-odds date and the one-in-ten date is narrower than at 52% of the 98 Arizona stations behind this site's ZIP pages.
In fall the first 32°F night comes by December 4 in half of years, as early as November 17 one year in ten, and holds off past December 19 one year in ten. A hard freeze of 28°F follows 13 days later, around December 17; in spring the one-in-ten date for 28°F is February 27, 19 days before the 32°F one. The freeze-free season lasts 279 days in a typical year, longer than at 63% of the 98 Arizona stations; it reaches 312 days one year in ten and falls short of 252 one year in ten. On average 20 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 19 days longer, to about March 17, and return around November 21. Nights of 24°F, cold enough to damage hardier plants, come in 57% of winters and 16°F in 1%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Feb 28 | Mar 5 | Mar 10 | Mar 13 | Mar 17 | Mar 22 | Mar 28 | Apr 2 | Apr 9 |
| 32°F | Jan 29 | Feb 6 | Feb 15 | Feb 20 | Feb 26 | Mar 2 | Mar 5 | Mar 9 | Mar 18 |
| 28°F97% of yrs | Dec 31 | Jan 8 | Jan 18 | Jan 28 | Feb 1 | Feb 6 | Feb 12 | Feb 20 | Feb 27 |
| 24°F57% of yrs | Dec 16 | Dec 26 | Jan 1 | Jan 6 | Jan 13 | Jan 22 | Jan 31 | Feb 5 | Feb 14 |
| 20°F11% 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 2 | Nov 9 | Nov 14 | Nov 18 | Nov 21 | Nov 24 | Nov 28 | Dec 1 | Dec 6 |
| 32°F | Nov 17 | Nov 23 | Nov 27 | Dec 1 | Dec 4 | Dec 6 | Dec 10 | Dec 13 | Dec 19 |
| 28°F97% of yrs | Nov 30 | Dec 5 | Dec 10 | Dec 14 | Dec 17 | Dec 22 | Dec 26 | Jan 1 | Jan 16 |
| 24°F57% of yrs | Dec 10 | Dec 17 | Dec 23 | Dec 28 | Jan 2 | Jan 8 | Jan 18 | Jan 28 | Feb 5 |
| 20°F11% of yrs | too rare for a date | ||||||||
| 16°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Tohono Chul, 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 85742 →Compare Tucson with another place →
Compared with the next station
The nearest other station, Catalina Sp, AZ, 8 miles east of Tucson and 180 feet higher, has a last frost 35 days later (April 2), a first frost 23 days earlier (November 11), a season 57 days shorter.
When it snows in Tucson, Arizona
Measurable snow is rare here: only 1 of 22 winters from 1991 to 2020 recorded 0.1 inch or more at Tucson U Of A #1, AZ, 9.3 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 85742
| When | What to do |
|---|---|
| December 18 – January 1 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 1 – January 15 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 29 – February 12 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 26 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 11 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 20 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 4 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 85742 is 5 miles from Tohono Chul, AZ, which stands at 2,527 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 85704 (Tucson). The 2023 USDA Plant Hardiness Zone Map lists ZIP 85742 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.