USDA Hardiness Zone 9a
Frost Dates for 85735 — Tucson, Arizona
NOAA 1991–2020 normals from Tucson 11 W, AZ (2,733 ft), 8 miles northeast.
Updated
In Tucson, the last spring frost (32°F) is around February 8 in half of years and has passed by March 8 in nine years out of ten. The first fall frost comes around December 10, as early as November 22 one year in ten, leaving a typical freeze-free season of 303 days (NOAA, Tucson 11 W, AZ).
- Last spring frost
- February 8
- First fall frost
- December 10
- Growing season
- 303 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
- 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 11 W, AZ see their last 32°F night by February 8; only one in ten is past it by January 6, and one in ten still has one after March 8. Planting tender crops after February 21 leaves a 30% risk of a frost on them, after March 1 20%, and after March 8 10%. The 28 days between the even-odds date and the one-in-ten date is wider than at 78% 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 10 in half of years, as early as November 22 one year in ten, and holds off past January 3 one year in ten. A hard freeze of 28°F follows 17 days later, around December 27; in spring the one-in-ten date for 28°F is February 18, 18 days before the 32°F one. The freeze-free season lasts 303 days in a typical year, longer than at 70% of the 98 Arizona stations; it reaches 339 days one year in ten and falls short of 270 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 24 days longer, to about March 4, and return around November 29. A 24°F night is unusual: 24% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Feb 6 | Feb 14 | Feb 22 | Feb 28 | Mar 4 | Mar 8 | Mar 13 | Mar 18 | Mar 29 |
| 32°F99% of yrs | Jan 6 | Jan 18 | Jan 30 | Feb 4 | Feb 8 | Feb 14 | Feb 21 | Mar 1 | Mar 8 |
| 28°F74% of yrs | Dec 15 | Dec 28 | Jan 4 | Jan 12 | Jan 20 | Jan 30 | Feb 3 | Feb 8 | Feb 18 |
| 24°F24% of yrs | too rare for a date | ||||||||
| 20°F3% 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 11 | Nov 16 | Nov 21 | Nov 25 | Nov 29 | Dec 1 | Dec 5 | Dec 9 | Dec 13 |
| 32°F99% of yrs | Nov 22 | Nov 28 | Dec 2 | Dec 6 | Dec 10 | Dec 13 | Dec 18 | Dec 24 | Jan 3 |
| 28°F74% of yrs | Nov 30 | Dec 9 | Dec 14 | Dec 20 | Dec 27 | Jan 1 | Jan 8 | Jan 19 | Feb 1 |
| 24°F24% of yrs | too rare for a date | ||||||||
| 20°F3% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Tucson 11 W, 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 85735 →Compare Tucson with another place →
Weather by month in Tucson
July is the warmest month at Tucson 11 W, AZ, averaging 99°F by day and 75°F at night; December is the coldest at 65°F and 40°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 57% of years and March still brings one in 20% of years.
Warmth for growing adds up to 7,376 growing degree days a year (base 50°F), more than at 65% of the 102 Arizona stations. 41% of them (3,020) have built up by the end of June, and July adds the most, 1,144. Precipitation totals 11.2 inches a year, most in July (2.2") 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 | 66 | 41 | 1.0 | 81% | 3 | 141 |
| Feb | 68 | 42 | 0.8 | 57% | 3 | 172 |
| Mar | 75 | 47 | 0.6 | 20% | <1 | 345 |
| Apr | 82 | 52 | 0.3 | 1% | 0 | 518 |
| May | 91 | 60 | 0.2 | 0% | 0 | 792 |
| Jun | 100 | 70 | 0.3 | 0% | 0 | 1051 |
| Jul | 99 | 75 | 2.2 | 0% | 0 | 1144 |
| Aug | 98 | 73 | 2.2 | 0% | 0 | 1105 |
| Sep | 94 | 69 | 1.0 | 0% | 0 | 954 |
| Oct | 86 | 58 | 0.8 | 0% | 0 | 681 |
| Nov | 74 | 48 | 0.8 | 25% | 1 | 341 |
| Dec | 65 | 40 | 1.0 | 84% | 5 | 131 |
Monthly normals 1991–2020 at Tucson 11 W, AZ (2,733 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 17 NW, AZ, 8 miles north of Tucson and 172 feet lower, has a last frost 15 days later (February 23), a first frost 4 days earlier (December 6), a season 16 days shorter.
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, 8.3 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 85735
| When | What to do |
|---|---|
| November 30 – December 14 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 14 – December 28 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 11 – January 25 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 8 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 17 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 26 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 10 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 85735 is 8 miles from Tucson 11 W, AZ, which stands at 2,733 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85735 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.