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Frost dates and planting calendar for Prescott, Arizona

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

USDA hardiness zone
7b[1]
Median last spring frost
Apr 30[2]
Median first fall frost
Oct 20[3]
Growing season, median
172 days[4]

Prescott, Arizona sits in USDA hardiness zone 7b at the city center[1]. The median last spring frost at the Prescott weather station is April 30[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 14, half of years Apr 30, 1 in 10 years after May 15Last frostmedian Apr 30First fall frost: 9 in 10 years before Nov 4, half of years Oct 20, 1 in 10 years before Oct 7First frostmedian Oct 20Frost riskHardyHardy vegetables: plant Apr 2 to Apr 16Apr 2 to Apr 16Semi-hardySemi-hardy vegetables: plant Apr 16 to Apr 30Apr 16 to Apr 30TenderTender vegetables: plant around Apr 30around Apr 30Very tenderVery tender vegetables: plant from May 14from May 14
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 Prescott weather station, using records from 1991 to 2020[5]. They are odds, not a forecast. In half of years the last spring frost comes after April 30, and in 1 of 10 years it comes after May 15[2]. In half of years the first fall frost comes before October 20, and in 1 of 10 years it comes before October 7[3]. The growing season was at least 172 days in half of years[4].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 14 after April 30 after May 15
First fall frost (32°F)[3] before October 7 before October 20 before November 4
  • Hard freeze (28°F): median last spring date April 13, median first fall date October 31[7].
  • Frost-free growing season: at least 153 days in 9 of 10 years, 172 days in half of years and 193 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 100% of years and 28°F or colder in 100% of years[8].
  • Weather station: Prescott (USC00026796), 1.7 miles from the city center, 5,205 feet, 30 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension wrote its vegetable planting guide for Colorado, so treat these dates as a starting point[6]. The GardenFacts calculation uses the NOAA median last frost of April 30 as the average last frost[6]. Hardy vegetables such as broccoli, lettuce and peas can go in as early as 2 to 4 weeks before that date, which works out to April 2 to April 16[6]. Semi-hardy vegetables such as carrots and potatoes can go in as early as 2 weeks before, up to the median date itself[9]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after the last frost, and the earliest start is May 14[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 30) is April 2 to April 16[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 30) is April 16, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 30[11]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 30), is May 14[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Apr 2 Jun 6 (from transplants)
Cabbage (hardy)[12] Apr 2 Jun 26 (from transplants)
Kohlrabi (hardy)[12] Apr 2 May 22
Lettuce (hardy)[12] Apr 2 Jun 1
Onions (hardy)[12] Apr 2 Jul 21
Peas (hardy)[12] Apr 2 Jun 6
Radishes (hardy)[12] Apr 2 May 2
Spinach (hardy)[12] Apr 2 May 12
Turnips (hardy)[12] Apr 2 May 22
Beets (semi-hardy)[12] Apr 16 Jun 15
Carrots (semi-hardy)[12] Apr 16 Jun 25
Cauliflower (semi-hardy)[12] Apr 16 not listed
Parsnips (semi-hardy)[12] Apr 16 Jun 25
Potatoes (semi-hardy)[12] Apr 16 Aug 19
Swiss chard (semi-hardy)[12] Apr 16 Jun 15
Snap beans (tender)[12] Apr 30 Jun 29
Sweet corn (tender)[12] Apr 30 Jun 29
Cucumbers (tender)[12] Apr 30 Jun 24
Summer squash (tender)[12] Apr 30 Jun 19
Cantaloupe (very tender)[12] May 14 Aug 7
Eggplant (very tender)[12] May 14 Jul 13 (from transplants)
Peppers (very tender)[12] May 14 Jul 23 (from transplants)
Tomatoes (very tender)[12] May 14 Jul 18 (from transplants)
Winter squash (very tender)[12] May 14 Aug 22
Watermelon (very tender)[12] May 14 Aug 7
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 7b means an average annual extreme minimum temperature of 5°F to 10°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]. About 98% of the city's land area is in ZIP code areas rated 7b, and 2% is in areas rated 8a[15].

Zone 7b: average annual extreme minimum temperature 5°F to 10°F (1991 to 2020)[1]. Modeled value at the city center: 8.1°F[1].

Share of the city's land area by ZIP code zone: zone 7b 98%, zone 8a 2%[15].

All towns in zone 7b and what zone 7b means

Zone by ZIP code
ZIP code Zone Coldest night range
86301[15] 7b 5 to 10°F
86305[15] 7b 5 to 10°F
86303[15] 7b 5 to 10°F
86323[15] 8a 10 to 15°F
86313[15] 7b 5 to 10°F
86315[15] 8a 10 to 15°F

Questions people ask

What growing zone is Prescott, Arizona?
The 2023 USDA map puts the center of Prescott in zone 7b[1]. By land area, 98% of the city lies in ZIP code areas rated 7b and 2% in areas rated 8a[15].
When is the last frost in Prescott?
The median last spring frost at the Prescott station is April 30, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after May 15[2].
When is the first frost in Prescott?
The median first fall frost is October 20, so in half of years the first frost comes before that date[3]. In 1 of 10 years it comes before October 7[3].
When to plant tomatoes in Prescott?
CSU Extension lists tomatoes as very tender and typically planted 2 or more weeks after the average last spring frost[10]. The earliest start by the GardenFacts calculation is May 14[10].
How long is the growing season in Prescott?
The growing season between the last spring and first fall frost was at least 172 days in half of years[4]. It was at least 153 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Prescott, Arizona in zone 7b. Zone 7b means an average annual extreme minimum temperature of 5°F to 10°F over 1991 to 2020. The map's modeled value at the city center is 8.1°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 April 14, in half of years after April 30, and in 1 of 10 years after May 15 (NOAA 1991 to 2020 normals). The median last frost date is April 30. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before October 7, in half of years before October 20, and in 9 of 10 years before November 4 (NOAA 1991 to 2020 normals). The median first frost date is October 20. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 153 days in 9 of 10 years, at least 172 days in half of years, and at least 193 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Prescott weather station (USC00026796), 1.7 miles from the center of Prescott at 5,205 feet, using 30 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 April 13 and the median first fall date is October 31. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 100% of years from 1991 to 2020, and 28°F or colder in 100% 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 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 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
  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. Prescott, Arizona overlaps 6 ZIP code areas. By land area, 98% lies in ZIP code areas rated zone 7b, 2% lies in ZIP code areas rated zone 8a. 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.