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Frost dates and planting calendar for Dublin, 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 15[2]
Median first fall frost
Dec 2[3]
Growing season, median
292 days[4]

The USDA map puts the center of Dublin, California in zone 9b[1]. The median last spring frost at the nearby NOAA station is February 15[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Jan 12, half of years Feb 15, 1 in 10 years after Mar 13Last frostmedian Feb 15First fall frost: 9 in 10 years before Dec 28, half of years Dec 2, 1 in 10 years before Nov 16First frostmedian Dec 2Frost riskHardyHardy vegetables: plant Jan 18 to Feb 1Jan 18 to Feb 1Semi-hardySemi-hardy vegetables: plant Feb 1 to Feb 15Feb 1 to Feb 15TenderTender vegetables: plant around Feb 15around Feb 15Very tenderVery tender vegetables: plant from Mar 1from Mar 1
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 dates come from NOAA climate normals for the Livermore weather station near Dublin[5]. In half of years the last spring frost comes after February 15, and in 1 of 10 years it comes after March 13[2]. In half of years the first fall frost comes before December 2, and in 1 of 10 years it comes before November 16[3]. These are odds from 1991 to 2020 records, 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 12 after February 15 after March 13
First fall frost (32°F)[3] before November 16 before December 2 before December 28
  • Hard freeze (28°F): median last spring date January 10, median first fall date December 18[7].
  • Frost-free growing season: at least 257 days in 9 of 10 years, 292 days in half of years and 330 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 99.3% of years and 28°F or colder in 76.1% of years[8].
  • Weather station: Livermore (USC00044997), 4.8 miles from the city center, 393 feet, 27 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]. CSU says hardy vegetables such as broccoli, lettuce and peas can go in as early as 2 to 4 weeks before the average last spring frost[6]. Using the NOAA median last frost of February 15, that works out to January 18 to February 1[6]. Tender vegetables such as snap beans and sweet corn can be planted from seed around the median last frost date, February 15[9]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after the average last frost, which gives an earliest start of March 1[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (February 15) is January 18 to February 1[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (February 15) is February 1, up to the median date itself[11]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, February 15[9]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (February 15), is March 1[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Jan 18 Mar 24 (from transplants)
Cabbage (hardy)[12] Jan 18 Apr 13 (from transplants)
Kohlrabi (hardy)[12] Jan 18 Mar 9
Lettuce (hardy)[12] Jan 18 Mar 19
Onions (hardy)[12] Jan 18 May 8
Peas (hardy)[12] Jan 18 Mar 24
Radishes (hardy)[12] Jan 18 Feb 17
Spinach (hardy)[12] Jan 18 Feb 27
Turnips (hardy)[12] Jan 18 Mar 9
Beets (semi-hardy)[12] Feb 1 Apr 2
Carrots (semi-hardy)[12] Feb 1 Apr 12
Cauliflower (semi-hardy)[12] Feb 1 not listed
Parsnips (semi-hardy)[12] Feb 1 Apr 12
Potatoes (semi-hardy)[12] Feb 1 Jun 6
Swiss chard (semi-hardy)[12] Feb 1 Apr 2
Snap beans (tender)[12] Feb 15 Apr 16
Sweet corn (tender)[12] Feb 15 Apr 16
Cucumbers (tender)[12] Feb 15 Apr 11
Summer squash (tender)[12] Feb 15 Apr 6
Cantaloupe (very tender)[12] Mar 1 May 25
Eggplant (very tender)[12] Mar 1 Apr 30 (from transplants)
Peppers (very tender)[12] Mar 1 May 10 (from transplants)
Tomatoes (very tender)[12] Mar 1 May 5 (from transplants)
Winter squash (very tender)[12] Mar 1 Jun 9
Watermelon (very tender)[12] Mar 1 May 25
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 the average coldest night of the winter is 25°F to 30°F, based on 1991 to 2020[1]. The zone is not about summer heat or frost dates[14]. All of Dublin's land area lies 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: 26.3°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
94568[15] 9b 25 to 30°F

Questions people ask

What growing zone is Dublin, California?
The 2023 USDA map puts the center of Dublin in zone 9b[1].
When is the last frost in Dublin, California?
At the nearby Livermore station, the median last spring frost is February 15[2]. In 1 of 10 years the last frost comes after March 13[2].
When to plant tomatoes in Dublin, California?
CSU says tomatoes typically go in 2 or more weeks after the average last spring frost[10]. Using the median last frost, the earliest start is March 1[10].
When is the first frost in Dublin, California?
At the Livermore station, the median first fall frost is December 2[3]. In 1 of 10 years it comes before November 16[3].
How long is the growing season in Dublin, California?
In half of years the growing season is at least 292 days[4]. In 9 of 10 years it is at least 257 days[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Dublin, 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 26.3°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 12, in half of years after February 15, and in 1 of 10 years after March 13 (NOAA 1991 to 2020 normals). The median last frost date is February 15. 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 16, in half of years before December 2, and in 9 of 10 years before December 28 (NOAA 1991 to 2020 normals). The median first frost date is December 2. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 257 days in 9 of 10 years, at least 292 days in half of years, and at least 330 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Livermore weather station (USC00044997), 4.8 miles from the center of Dublin at 393 feet, using 27 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 10 and the median first fall date is December 18. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 99.3% of years from 1991 to 2020, and 28°F or colder in 76.1% 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. Dublin, California overlaps 1 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.