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Frost dates and planting calendar for Vacaville, California

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 18[2]
Median first fall frost
Nov 28[3]
Growing season, median
283 days[4]

Vacaville is in USDA hardiness zone 9b[1]. The median last spring frost is February 18, which means that in half of years the last frost comes after that date[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Jan 11, half of years Feb 18, 1 in 10 years after Mar 25Last frostmedian Feb 18First fall frost: 9 in 10 years before Dec 18, half of years Nov 28, 1 in 10 years before Nov 12First frostmedian Nov 28Frost riskHardyHardy vegetables: plant Jan 21 to Feb 4Jan 21 to Feb 4Semi-hardySemi-hardy vegetables: plant Feb 4 to Feb 18Feb 4 to Feb 18TenderTender vegetables: plant around Feb 18around Feb 18Very tenderVery tender vegetables: plant from Mar 4from Mar 4
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.

NOAA frost dates for Vacaville come from the Vacaville Nut Tree Airport weather station, using records from 1991 to 2020[5]. In half of years the last spring frost comes after February 18, and in 1 of 10 years it comes after March 25[2]. In half of years the first fall frost comes before November 28, and in 1 of 10 years it comes before November 12[3]. These are chances from past records and not a forecast, so any year can be earlier or later[5].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after January 11 after February 18 after March 25
First fall frost (32°F)[3] before November 12 before November 28 before December 18
  • Hard freeze (28°F): median last spring date January 15, median first fall date December 10[7].
  • Frost-free growing season: at least 245 days in 9 of 10 years, 283 days in half of years and 325 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 99.6% of years and 28°F or colder in 86.2% of years[8].
  • Weather station: Vacaville Nut Tree Airport (USW00093241), 1.4 miles from the city center, 109 feet, 17 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension groups vegetables by how well they handle frost, and its guide was written for Colorado[6]. GardenFacts takes the NOAA median last frost of February 18 as the average last frost[6]. Hardy vegetables such as lettuce, peas and spinach can go in as early as 2 to 4 weeks before that date, which is January 21 to February 4[6]. Tender vegetables such as snap beans and sweet corn can be planted from seed around February 18[9]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after the last frost, so the earliest start is March 4[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (February 18) is January 21 to February 4[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (February 18) is February 4, up to the median date itself[11]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, February 18[9]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (February 18), is March 4[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Jan 21 Mar 27 (from transplants)
Cabbage (hardy)[12] Jan 21 Apr 16 (from transplants)
Kohlrabi (hardy)[12] Jan 21 Mar 12
Lettuce (hardy)[12] Jan 21 Mar 22
Onions (hardy)[12] Jan 21 May 11
Peas (hardy)[12] Jan 21 Mar 27
Radishes (hardy)[12] Jan 21 Feb 20
Spinach (hardy)[12] Jan 21 Mar 2
Turnips (hardy)[12] Jan 21 Mar 12
Beets (semi-hardy)[12] Feb 4 Apr 5
Carrots (semi-hardy)[12] Feb 4 Apr 15
Cauliflower (semi-hardy)[12] Feb 4 not listed
Parsnips (semi-hardy)[12] Feb 4 Apr 15
Potatoes (semi-hardy)[12] Feb 4 Jun 9
Swiss chard (semi-hardy)[12] Feb 4 Apr 5
Snap beans (tender)[12] Feb 18 Apr 19
Sweet corn (tender)[12] Feb 18 Apr 19
Cucumbers (tender)[12] Feb 18 Apr 14
Summer squash (tender)[12] Feb 18 Apr 9
Cantaloupe (very tender)[12] Mar 4 May 28
Eggplant (very tender)[12] Mar 4 May 3 (from transplants)
Peppers (very tender)[12] Mar 4 May 13 (from transplants)
Tomatoes (very tender)[12] Mar 4 May 8 (from transplants)
Winter squash (very tender)[12] Mar 4 Jun 12
Watermelon (very tender)[12] Mar 4 May 28
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

The USDA zone is based on the average coldest night of each winter from 1991 to 2020, not on summer heat or frost dates[14]. Zone 9b means an average yearly extreme low of 25°F to 30°F[1]. Vacaville overlaps 5 ZIP code areas, and by land area 100% of the city is in zone 9b ZIP code areas[15].

Zone 9b: average annual extreme minimum temperature 25°F to 30°F (1991 to 2020)[1]. Modeled value at the city center: 25.8°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
95687[15] 9b 25 to 30°F
95688[15] 9b 25 to 30°F
94533[15] 9b 25 to 30°F
94534[15] 9b 25 to 30°F
95620[15] 9b 25 to 30°F

Questions people ask

What growing zone is Vacaville?
The center of Vacaville is in USDA zone 9b on the 2023 map[1]. All of the city by land area is in ZIP code areas rated 9b[15].
When is the last frost in Vacaville?
The median last spring frost is February 18, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after March 25[2].
When to plant tomatoes in Vacaville?
CSU Extension says tomatoes are very tender and typically go in 2 or more weeks after the average last frost[10]. Using the median last frost, the earliest start is March 4[10].
When is the first frost in Vacaville?
The median first fall frost is November 28, so in half of years the first frost comes before that date[3]. In 1 of 10 years it comes before November 12[3].
How long is the growing season in Vacaville?
The growing season is at least 283 days in half of years[4]. It is at least 245 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Vacaville, California 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 25.8°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 11, in half of years after February 18, and in 1 of 10 years after March 25 (NOAA 1991 to 2020 normals). The median last frost date is February 18. 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 12, in half of years before November 28, and in 9 of 10 years before December 18 (NOAA 1991 to 2020 normals). The median first frost date is November 28. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 245 days in 9 of 10 years, at least 283 days in half of years, and at least 325 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Vacaville Nut Tree Airport weather station (USW00093241), 1.4 miles from the center of Vacaville at 109 feet, using 17 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 15 and the median first fall date is December 10. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 99.6% of years from 1991 to 2020, and 28°F or colder in 86.2% 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. Vacaville, California overlaps 5 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.