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Frost dates and planting calendar for Tucson, Arizona

Updated October 30, 2026. Based on USDA, NOAA and Colorado State University Extension data. Published by Humblebee.

USDA hardiness zone
9b[1]
Median last spring frost
Feb 5[2]
Median first fall frost
Dec 9[3]
Growing season, median
307 days[4]

The USDA map puts the center of Tucson in hardiness zone 9b[1]. NOAA records show the median last spring frost at the Tucson airport is February 5[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Jan 4, half of years Feb 5, 1 in 10 years after Mar 2Last frostmedian Feb 5First frostmedian Dec 9Frost riskHardyHardy vegetables: plant Jan 8 to Jan 22Jan 8 to Jan 22Semi-hardySemi-hardy vegetables: plant Jan 22 to Feb 5Jan 22 to Feb 5TenderTender vegetables: plant around Feb 5around Feb 5Very tenderVery tender vegetables: plant from Feb 19from Feb 19
Shaded: the span between the dates frost passes in 9 of 10 years and 1 of 10 years[2][3]. Green: planting windows from the CSU rules applied to the median last frost (GardenFacts calculation)[6]. Exact dates are in the tables below.

Frost dates here come from NOAA climate normals for the Tucson International Airport weather station, using records from 1991 to 2020[5]. In half of years the last spring frost comes after February 5, and in 1 of 10 years it comes after March 2[2]. In fall, the first frost comes before December 9 in half of years and before November 21 in 1 of 10 years[3]. These are chances, not promises. Any year can be earlier or later.

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after January 4 after February 5 after March 2
First fall frost (32°F)[3] before November 21 before December 9 before January 3
  • Hard freeze (28°F): median last spring date January 11, median first fall date December 26[7].
  • Frost-free growing season: at least 274 days in 9 of 10 years, 307 days in half of years and 344 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 98.9% of years and 28°F or colder in 69.6% of years[8].
  • Weather station: Tucson International Airport (USW00023160), 5.2 miles from the city center, 2,549 feet, 29 years of 1991 to 2020 records[5].

When to plant vegetables

The planting dates on this page use Colorado State University Extension's vegetable guide, which was written for Colorado[6]. GardenFacts takes the median last frost, February 5, as the average last frost[6]. Hardy vegetables like lettuce, peas and spinach can go in as early as January 8 to January 22[6]. Tender vegetables like snap beans and sweet corn go in from seed around February 5[9]. Very tender crops like tomatoes and peppers typically wait 2 or more weeks after the average last frost, so the GardenFacts earliest start is February 19[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (February 5) is January 8 to January 22[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (February 5) is January 22, up to the median date itself[11]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, February 5[9]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (February 5), is February 19[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Jan 8 Mar 14 (from transplants)
Cabbage (hardy)[12] Jan 8 Apr 3 (from transplants)
Kohlrabi (hardy)[12] Jan 8 Feb 27
Lettuce (hardy)[12] Jan 8 Mar 9
Onions (hardy)[12] Jan 8 Apr 28
Peas (hardy)[12] Jan 8 Mar 14
Radishes (hardy)[12] Jan 8 Feb 7
Spinach (hardy)[12] Jan 8 Feb 17
Turnips (hardy)[12] Jan 8 Feb 27
Beets (semi-hardy)[12] Jan 22 Mar 23
Carrots (semi-hardy)[12] Jan 22 Apr 2
Cauliflower (semi-hardy)[12] Jan 22 not listed
Parsnips (semi-hardy)[12] Jan 22 Apr 2
Potatoes (semi-hardy)[12] Jan 22 May 27
Swiss chard (semi-hardy)[12] Jan 22 Mar 23
Snap beans (tender)[12] Feb 5 Apr 6
Sweet corn (tender)[12] Feb 5 Apr 6
Cucumbers (tender)[12] Feb 5 Apr 1
Summer squash (tender)[12] Feb 5 Mar 27
Cantaloupe (very tender)[12] Feb 19 May 15
Eggplant (very tender)[12] Feb 19 Apr 20 (from transplants)
Peppers (very tender)[12] Feb 19 Apr 30 (from transplants)
Tomatoes (very tender)[12] Feb 19 Apr 25 (from transplants)
Winter squash (very tender)[12] Feb 19 May 30
Watermelon (very tender)[12] Feb 19 May 15
Spacing, depth and soil temperature (CSU Extension)
Vegetable Min. soil temp Depth Spacing Days to harvest
Broccoli[13] 40°F 1/2 in 18 in 65
Cabbage[13] 40°F 1/2 in 18 in 85
Kohlrabi[13] 40°F 1/2 in 7-9 in 50
Lettuce[13] 35°F 1/4 in 7-9 in 60
Onions[13] 35°F 1/4 in (seed), 1-2 in (sets) 4-6 in 110
Peas[13] 40°F 1 in 4-6 in 65
Radishes[13] 40°F 1/2 in 2-3 in 30
Spinach[13] 40°F 1/2 in 4-6 in 40
Turnips[13] 40°F 1/2 in 4-6 in 50
Beets[13] 40°F 3/4-1 in 4-6 in 60
Carrots[13] 40°F 1/4 in 2-3 in 70
Cauliflower[13] 40°F 1/2 in 18 in –
Parsnips[13] 35°F 1/2 in 5-6 in 70
Potatoes[13] 45°F – – 125
Swiss chard[13] 40°F 1 in 7-9 in 60
Snap beans[13] 55°F 1-1 1/2 in 6 in 60
Sweet corn[13] 50°F 1-1 1/2 in 12 x 30 in or 9 x 36 in 60-90
Cucumbers[13] 60°F 1 in 6 in trellised, 24-36 in untrellised 55
Summer squash[13] 60°F 1-1 1/2 in 36-48 in 50
Cantaloupe[13] 60°F 1-1 1/2 in 36-48 in 85
Eggplant[13] 60°F 1/4 in 18-24 in 60
Peppers[13] 60°F 1/4 in 15-18 in 70
Tomatoes[13] 50°F 1/4 in 24 in trellised 65
Winter squash[13] 60°F 1-1 1/2 in 36-48 in 100
Watermelon[13] 60°F 1-1 1/2 in 36-48 in 85

Hardiness zone

A hardiness zone is based on the average coldest winter night, not on summer heat or frost dates[14]. Zone 9b means the coldest night of the year averages 25°F to 30°F[1]. Tucson spans two zones[15]. By land area, 55% lies in ZIP code areas rated zone 9a and 45% in ZIP code areas rated zone 9b[15].

Zone 9b: average annual extreme minimum temperature 25°F to 30°F (1991 to 2020)[1]. Modeled value at the city center: 26°F[1].

Share of the city's land area by ZIP code zone: zone 9a 55%, zone 9b 45%[15].

All towns in zone 9b and what zone 9b means

Zone by ZIP code
ZIP code Zone Coldest night range
85756[15] 9a 20 to 25°F
85747[15] 9a 20 to 25°F
85745[15] 9b 25 to 30°F
85713[15] 9b 25 to 30°F
85710[15] 9b 25 to 30°F
85730[15] 9a 20 to 25°F
85705[15] 9b 25 to 30°F
85706[15] 9b 25 to 30°F
85711[15] 9b 25 to 30°F
85641[15] 9a 20 to 25°F
85719[15] 9b 25 to 30°F
85716[15] 9b 25 to 30°F
85712[15] 9b 25 to 30°F
85748[15] 9a 20 to 25°F
85715[15] 9b 25 to 30°F
85714[15] 9b 25 to 30°F
85707[15] 9b 25 to 30°F
85746[15] 9a 20 to 25°F
85708[15] 9b 25 to 30°F
85749[15] 9a 20 to 25°F
85701[15] 9b 25 to 30°F
85734[15] 9a 20 to 25°F
85718[15] 9a 20 to 25°F
85709[15] 9b 25 to 30°F
85704[15] 9a 20 to 25°F
85741[15] 9a 20 to 25°F
85723[15] 9b 25 to 30°F
85743[15] 9b 25 to 30°F
85724[15] 9b 25 to 30°F
85726[15] 9b 25 to 30°F

Questions people ask

What growing zone is Tucson, Arizona?
The 2023 USDA map puts the center of Tucson in zone 9b[1]. By land area, 55% of the city lies in ZIP code areas rated zone 9a[15].
When is the last frost in Tucson?
At the Tucson airport station, the median last spring frost date is February 5[2]. In 1 of 10 years the last frost comes after March 2[2].
When to plant tomatoes in Tucson?
CSU Extension says tomatoes typically go in 2 or more weeks after the average last frost[10]. For Tucson the earliest start works out to February 19[10].
When is the first frost in Tucson?
The median first fall frost date is December 9[3]. In 1 of 10 years the first frost comes before November 21[3].
How long is the growing season in Tucson?
In half of years the growing season is at least 307 days[4]. In 9 of 10 years it is at least 274 days[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Tucson, Arizona in zone 9b. Zone 9b means an average annual extreme minimum temperature of 25°F to 30°F over 1991 to 2020. The map's modeled value at the city center is 26°F. USDA zone map 2023 (PRISM, OSU)
  2. Last spring frost (32°F) at this station: in 9 of 10 years the last frost comes after January 4, in half of years after February 5, and in 1 of 10 years after March 2 (NOAA 1991 to 2020 normals). The median last frost date is February 5. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before November 21, in half of years before December 9, and in 9 of 10 years before January 3 (NOAA 1991 to 2020 normals). The median first frost date is December 9. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 274 days in 9 of 10 years, at least 307 days in half of years, and at least 344 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Tucson International Airport weather station (USW00023160), 5.2 miles from the center of Tucson at 2,549 feet, using 29 years of records from 1991 to 2020. NOAA Climate Normals 1991-2020
  6. Colorado State University Extension's vegetable planting guide (written for Colorado) groups broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips as hardy vegetables, with this rule: as early as 2-4 weeks before the average last... CSU Extension GardenNotes #720
  7. Hard freeze (28°F) at this station: the median last spring date is January 11 and the median first fall date is December 26. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 98.9% of years from 1991 to 2020, and 28°F or colder in 69.6% of years. NOAA Climate Normals 1991-2020
  9. Colorado State University Extension's vegetable planting guide (written for Colorado) groups snap beans, sweet corn, cucumbers, summer squash as tender vegetables, with this rule: from seed around the average last spring frost; cucumber and summer squash... CSU Extension GardenNotes #720
  10. Colorado State University Extension's vegetable planting guide (written for Colorado) groups cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon as very tender vegetables, with this rule: typically 2 or more weeks after the average last... CSU Extension GardenNotes #720
  11. Colorado State University Extension's vegetable planting guide (written for Colorado) groups beets, carrots, cauliflower, parsnips, potatoes, Swiss chard as semi-hardy vegetables, with this rule: as early as 0-2 weeks before the average last spring frost.... CSU Extension GardenNotes #720
  12. GardenFacts calculation: earliest planting date plus CSU days to harvest (table on this page), from the station's median last frost. NOAA Climate Normals 1991-2020
  13. CSU Extension vegetable table: soil temperature, depth, spacing, days to harvest (table on this page). CSU Extension GardenNotes #720
  14. USDA hardiness zones are based on the average annual extreme minimum winter temperature (the coldest night of each winter, averaged over 1991 to 2020 for the 2023 map), not on summer heat or frost dates. Each zone spans 10°F and each half zone (a or b)... USDA Plant Hardiness Zone Map
  15. Tucson, Arizona overlaps 30 ZIP code areas. By land area, 55% lies in ZIP code areas rated zone 9a, 45% lies in ZIP code areas rated zone 9b. USDA zone map 2023 (PRISM, OSU)

Frost dates are probabilities from 1991 to 2020 weather records at one NOAA station, not a forecast. Any year can be earlier or later. The hardiness zone describes the average coldest winter night, not frost dates or summer heat. Spots inside the city can differ (ZIP table). Planting rules come from Colorado State University Extension's guide, written for Colorado. A local extension office may give dates tuned to the area. Planting and harvest dates marked GardenFacts calculation are simple arithmetic from the facts above, not advice from the source.

Hardiness zone data: USDA Plant Hardiness Zone Map (2023), USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu, accessed October 30, 2026. This is not the official USDA map. Frost data: NOAA NCEI U.S. Climate Normals 1991-2020. Planting rules: Colorado State University Extension.