GardenFacts

All states › California › Santa Rosa

Frost dates and planting calendar for Santa Rosa, 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 25[2]
Median first fall frost
Dec 1[3]
Growing season, median
279 days[4]

The center of Santa Rosa is in USDA hardiness zone 9b on the 2023 map[1]. The median last spring frost at the nearby NOAA station is February 25[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Jan 21, half of years Feb 25, 1 in 10 years after Mar 29Last frostmedian Feb 25First fall frost: 9 in 10 years before Dec 24, half of years Dec 1, 1 in 10 years before Nov 10First frostmedian Dec 1Frost riskHardyHardy vegetables: plant Jan 28 to Feb 11Jan 28 to Feb 11Semi-hardySemi-hardy vegetables: plant Feb 11 to Feb 25Feb 11 to Feb 25TenderTender vegetables: plant around Feb 25around Feb 25Very tenderVery tender vegetables: plant from Mar 11from Mar 11
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 Santa Rosa weather station, using records from 1991 to 2020[5]. In half of years the last spring frost comes after February 25, and in 1 of 10 years it comes after March 29[2]. In half of years the first fall frost comes before December 1, and in 1 of 10 years it comes before November 10[3]. These are odds from past records and not promises, so 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 21 after February 25 after March 29
First fall frost (32°F)[3] before November 10 before December 1 before December 24
  • Hard freeze (28°F): median last spring date January 20, median first fall date December 16[7].
  • Frost-free growing season: at least 244 days in 9 of 10 years, 279 days in half of years and 319 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 99.4% of years and 28°F or colder in 83% of years[8].
  • Weather station: Santa Rosa (USC00047965), 0.8 miles from the city center, 166 feet, 22 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension's planting guide was written for Colorado, so treat these dates as a starting point[6]. Hardy vegetables such as broccoli, lettuce and peas can go in as early as 2 to 4 weeks before the median last frost, which is January 28 to February 11[6]. Semi-hardy vegetables such as carrots and potatoes can go in as early as 2 weeks before the median last frost, from February 11 up to the median date[9]. Tender vegetables such as snap beans and sweet corn can be sown from seed around February 25[10]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after the median last frost, so the earliest start is March 11[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (February 25) is January 28 to February 11[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (February 25) is February 11, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, February 25[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (February 25), is March 11[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Jan 28 Apr 3 (from transplants)
Cabbage (hardy)[12] Jan 28 Apr 23 (from transplants)
Kohlrabi (hardy)[12] Jan 28 Mar 19
Lettuce (hardy)[12] Jan 28 Mar 29
Onions (hardy)[12] Jan 28 May 18
Peas (hardy)[12] Jan 28 Apr 3
Radishes (hardy)[12] Jan 28 Feb 27
Spinach (hardy)[12] Jan 28 Mar 9
Turnips (hardy)[12] Jan 28 Mar 19
Beets (semi-hardy)[12] Feb 11 Apr 12
Carrots (semi-hardy)[12] Feb 11 Apr 22
Cauliflower (semi-hardy)[12] Feb 11 not listed
Parsnips (semi-hardy)[12] Feb 11 Apr 22
Potatoes (semi-hardy)[12] Feb 11 Jun 16
Swiss chard (semi-hardy)[12] Feb 11 Apr 12
Snap beans (tender)[12] Feb 25 Apr 26
Sweet corn (tender)[12] Feb 25 Apr 26
Cucumbers (tender)[12] Feb 25 Apr 21
Summer squash (tender)[12] Feb 25 Apr 16
Cantaloupe (very tender)[12] Mar 11 Jun 4
Eggplant (very tender)[12] Mar 11 May 10 (from transplants)
Peppers (very tender)[12] Mar 11 May 20 (from transplants)
Tomatoes (very tender)[12] Mar 11 May 15 (from transplants)
Winter squash (very tender)[12] Mar 11 Jun 19
Watermelon (very tender)[12] Mar 11 Jun 4
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 coldest night of the year between 25°F and 30°F over 1991 to 2020[1]. The zone is based on winter lows, not on summer heat or frost dates[14]. Santa Rosa is not all one zone[15]. By land area, 62% lies in ZIP code areas rated zone 9a and 38% in 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: 25.2°F[1].

Share of the city's land area by ZIP code zone: zone 9a 62%, zone 9b 38%[15].

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

Zone by ZIP code
ZIP code Zone Coldest night range
95409[15] 9b 25 to 30°F
95404[15] 9b 25 to 30°F
95407[15] 9a 20 to 25°F
95403[15] 9a 20 to 25°F
95401[15] 9a 20 to 25°F
95405[15] 9a 20 to 25°F
95472[15] 9a 20 to 25°F

Questions people ask

What growing zone is Santa Rosa?
The center of Santa Rosa is in USDA zone 9b on the 2023 map[1]. Some ZIP code areas are rated 9a[15].
When is the last frost in Santa Rosa?
The median last spring frost is February 25, meaning in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after March 29[2].
When to plant tomatoes in Santa Rosa?
CSU Extension says tomatoes typically go in 2 or more weeks after the average last spring frost[11]. Using the median last frost, the earliest start is March 11[11].
When is the first frost in Santa Rosa?
The median first fall frost is December 1, so in half of years it comes before that date[3]. In 1 of 10 years it comes before November 10[3].
How long is the growing season in Santa Rosa?
In half of years the season between the last spring and first fall frost is at least 279 days[4]. In 9 of 10 years it is at least 244 days[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Santa Rosa, 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 25.2°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 21, in half of years after February 25, and in 1 of 10 years after March 29 (NOAA 1991 to 2020 normals). The median last frost date is February 25. 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 10, in half of years before December 1, and in 9 of 10 years before December 24 (NOAA 1991 to 2020 normals). The median first frost date is December 1. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 244 days in 9 of 10 years, at least 279 days in half of years, and at least 319 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Santa Rosa weather station (USC00047965), 0.8 miles from the center of Santa Rosa at 166 feet, using 22 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 20 and the median first fall date is December 16. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 99.4% of years from 1991 to 2020, and 28°F or colder in 83% 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. Santa Rosa, California overlaps 7 ZIP code areas. By land area, 62% lies in ZIP code areas rated zone 9a, 38% 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.