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Frost dates and planting calendar for Gilbert, 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 1[2]
Median first fall frost
Dec 10[3]
Growing season, median
312 days[4]

The USDA 2023 map puts the center of Gilbert, Arizona in zone 9b[1]. The median last spring frost at the E Mesa NOAA station is February 1[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Jan 1, half of years Feb 1, 1 in 10 years after Feb 28Last frostmedian Feb 1First frostmedian Dec 10Frost riskHardyHardy vegetables: plant Jan 4 to Jan 18Jan 4 to Jan 18Semi-hardySemi-hardy vegetables: plant Jan 18 to Feb 1Jan 18 to Feb 1TenderTender vegetables: plant around Feb 1around Feb 1Very tenderVery tender vegetables: plant from Feb 15from Feb 15
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.

These frost dates come from NOAA climate normals for the E Mesa weather station near Gilbert[5]. They use records from 1991 to 2020[5]. In half of years the last spring frost comes after February 1, and in 1 of 10 years it comes after February 28[2]. In half of years the first fall frost comes before December 10, and in 1 of 10 years it comes before November 22[3]. These are odds from past records, not a forecast, so any year can be earlier or later[2].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after January 1 after February 1 after February 28
First fall frost (32°F)[3] before November 22 before December 10 before January 1
  • Hard freeze (28°F): median last spring date January 11, median first fall date December 26[7].
  • Frost-free growing season: at least 280 days in 9 of 10 years, 312 days in half of years and 348 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 98.2% of years and 28°F or colder in 70.1% of years[8].
  • Weather station: E Mesa (USC00022782), 9.4 miles from the city center, 1,518 feet, 15 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension wrote its vegetable planting guide for Colorado, so these dates are simple arithmetic from its rules and not advice from CSU[6]. CSU's hardy vegetables, such as broccoli, lettuce and spinach, can go in as early as 2 to 4 weeks before the median last frost, which works out to January 4 to January 18 in Gilbert[6]. Semi-hardy vegetables, such as carrots and potatoes, can go in as early as 2 weeks before the median last frost, which is January 18[9]. Tender vegetables, such as snap beans and sweet corn, are planted from seed around the median last frost date, February 1[10]. Very tender vegetables, such as tomatoes and peppers, typically wait 2 or more weeks after it, so the earliest start is February 15[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (February 1) is January 4 to January 18[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (February 1) is January 18, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, February 1[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (February 1), is February 15[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Jan 4 Mar 10 (from transplants)
Cabbage (hardy)[12] Jan 4 Mar 30 (from transplants)
Kohlrabi (hardy)[12] Jan 4 Feb 23
Lettuce (hardy)[12] Jan 4 Mar 5
Onions (hardy)[12] Jan 4 Apr 24
Peas (hardy)[12] Jan 4 Mar 10
Radishes (hardy)[12] Jan 4 Feb 3
Spinach (hardy)[12] Jan 4 Feb 13
Turnips (hardy)[12] Jan 4 Feb 23
Beets (semi-hardy)[12] Jan 18 Mar 19
Carrots (semi-hardy)[12] Jan 18 Mar 29
Cauliflower (semi-hardy)[12] Jan 18 not listed
Parsnips (semi-hardy)[12] Jan 18 Mar 29
Potatoes (semi-hardy)[12] Jan 18 May 23
Swiss chard (semi-hardy)[12] Jan 18 Mar 19
Snap beans (tender)[12] Feb 1 Apr 2
Sweet corn (tender)[12] Feb 1 Apr 2
Cucumbers (tender)[12] Feb 1 Mar 28
Summer squash (tender)[12] Feb 1 Mar 23
Cantaloupe (very tender)[12] Feb 15 May 11
Eggplant (very tender)[12] Feb 15 Apr 16 (from transplants)
Peppers (very tender)[12] Feb 15 Apr 26 (from transplants)
Tomatoes (very tender)[12] Feb 15 Apr 21 (from transplants)
Winter squash (very tender)[12] Feb 15 May 26
Watermelon (very tender)[12] Feb 15 May 11
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

Zone 9b means an average annual extreme minimum temperature of 25°F to 30°F over 1991 to 2020[1]. The zone is based on the coldest night of each winter, not on summer heat or frost dates[14]. By land area, 100% of Gilbert lies in ZIP code areas rated zone 9b, so no part of the city lies in a ZIP code area rated a different zone[15].

Zone 9b: average annual extreme minimum temperature 25°F to 30°F (1991 to 2020)[1]. Modeled value at the city center: 27.9°F[1].

Share of the city's land area by ZIP code zone: zone 9b 100%[15].

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

Zone by ZIP code
ZIP code Zone Coldest night range
85298[15] 9b 25 to 30°F
85234[15] 9b 25 to 30°F
85295[15] 9b 25 to 30°F
85296[15] 9b 25 to 30°F
85297[15] 9b 25 to 30°F
85233[15] 9b 25 to 30°F
85142[15] 9b 25 to 30°F
85212[15] 9b 25 to 30°F
85206[15] 9b 25 to 30°F
85209[15] 9b 25 to 30°F
85236[15] 9b 25 to 30°F
85225[15] 9b 25 to 30°F
85249[15] 9b 25 to 30°F

Questions people ask

What growing zone is Gilbert, Arizona?
The 2023 USDA Plant Hardiness Zone Map puts the center of Gilbert in zone 9b[1]. By land area, all of the city lies in ZIP code areas rated 9b[15].
When is the last frost in Gilbert?
The median last spring frost at the E Mesa NOAA station is February 1, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after February 28[2].
When to plant tomatoes in Gilbert?
CSU Extension groups tomatoes as very tender, typically planted 2 or more weeks after the average last spring frost[11]. Using the median last frost of February 1, the earliest start is February 15[11].
When is the first frost in Gilbert?
The median first fall frost at the station is December 10, so in half of years the first frost comes before that date[3]. In 1 of 10 years it comes before November 22[3].
How long is the growing season in Gilbert?
The season between the last spring and first fall frost is at least 312 days in half of years[4]. It is at least 280 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Gilbert, 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 27.9°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 1, in half of years after February 1, and in 1 of 10 years after February 28 (NOAA 1991 to 2020 normals). The median last frost date is February 1. 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 22, in half of years before December 10, and in 9 of 10 years before January 1 (NOAA 1991 to 2020 normals). The median first frost date is December 10. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 280 days in 9 of 10 years, at least 312 days in half of years, and at least 348 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the E Mesa weather station (USC00022782), 9.4 miles from the center of Gilbert at 1,518 feet, using 15 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 98.2% of years from 1991 to 2020, and 28°F or colder in 70.1% of years. NOAA Climate Normals 1991-2020
  9. 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
  10. 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
  11. 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
  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. Gilbert, Arizona overlaps 13 ZIP code areas. By land area, 100% 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.