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Frost dates and planting calendar for San Antonio, Texas

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

USDA hardiness zone
9a[1]
Median last spring frost
Feb 26[2]
Median first fall frost
Nov 28[3]
Growing season, median
277 days[4]

The USDA 2023 map puts the center of San Antonio in zone 9a[1]. NOAA records from 1991 to 2020 give a median last spring frost of February 26 at the airport station[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Jan 29, half of years Feb 26, 1 in 10 years after Mar 17Last frostmedian Feb 26First fall frost: 9 in 10 years before Dec 22, half of years Nov 28, 1 in 10 years before Nov 7First frostmedian Nov 28Frost riskHardyHardy vegetables: plant Jan 29 to Feb 12Jan 29 to Feb 12Semi-hardySemi-hardy vegetables: plant Feb 12 to Feb 26Feb 12 to Feb 26TenderTender vegetables: plant around Feb 26around Feb 26Very tenderVery tender vegetables: plant from Mar 12from Mar 12
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 are odds from NOAA records for 1991 to 2020, not a forecast. They come from the San Antonio International Airport weather station[5]. In 9 of 10 years the last spring frost comes after January 29, in half of years after February 26, and in 1 of 10 years after March 17[2]. In 1 of 10 years the first fall frost comes before November 7, in half of years before November 28, and in 9 of 10 years before December 22[3]. Any single year can come 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 29 after February 26 after March 17
First fall frost (32°F)[3] before November 7 before November 28 before December 22
  • Hard freeze (28°F): median last spring date February 9, median first fall date December 13[7].
  • Frost-free growing season: at least 247 days in 9 of 10 years, 277 days in half of years and 311 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 99.9% of years and 28°F or colder in 95.9% of years[8].
  • Weather station: San Antonio International Airport (USW00012921), 6.1 miles from the city center, 789 feet, 27 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension groups vegetables by how well they handle cold. Its guide was written for Colorado, so the dates here are simple arithmetic and not advice from CSU[6]. We use the NOAA median last frost of February 26 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 it, which is January 29 to February 12[6]. Semi-hardy vegetables such as beets, carrots and potatoes can go in as early as 2 weeks before it, which is February 12[9]. Very tender vegetables such as tomatoes and peppers typically wait 2 or more weeks after it, so the earliest start is March 12[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (February 26) is January 29 to February 12[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (February 26) is February 12, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, February 26[11]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (February 26), is March 12[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Jan 29 Apr 4 (from transplants)
Cabbage (hardy)[12] Jan 29 Apr 24 (from transplants)
Kohlrabi (hardy)[12] Jan 29 Mar 20
Lettuce (hardy)[12] Jan 29 Mar 30
Onions (hardy)[12] Jan 29 May 19
Peas (hardy)[12] Jan 29 Apr 4
Radishes (hardy)[12] Jan 29 Feb 28
Spinach (hardy)[12] Jan 29 Mar 10
Turnips (hardy)[12] Jan 29 Mar 20
Beets (semi-hardy)[12] Feb 12 Apr 13
Carrots (semi-hardy)[12] Feb 12 Apr 23
Cauliflower (semi-hardy)[12] Feb 12 not listed
Parsnips (semi-hardy)[12] Feb 12 Apr 23
Potatoes (semi-hardy)[12] Feb 12 Jun 17
Swiss chard (semi-hardy)[12] Feb 12 Apr 13
Snap beans (tender)[12] Feb 26 Apr 27
Sweet corn (tender)[12] Feb 26 Apr 27
Cucumbers (tender)[12] Feb 26 Apr 22
Summer squash (tender)[12] Feb 26 Apr 17
Cantaloupe (very tender)[12] Mar 12 Jun 5
Eggplant (very tender)[12] Mar 12 May 11 (from transplants)
Peppers (very tender)[12] Mar 12 May 21 (from transplants)
Tomatoes (very tender)[12] Mar 12 May 16 (from transplants)
Winter squash (very tender)[12] Mar 12 Jun 20
Watermelon (very tender)[12] Mar 12 Jun 5
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 9a means the coldest night of each winter averages 20°F to 25°F over 1991 to 2020[1]. The zone is about winter lows, not summer heat or frost dates[14]. Most of the city, 94% of its land area, sits in ZIP code areas rated 9a, and 6% sits in areas rated 8b[15].

Zone 9a: average annual extreme minimum temperature 20°F to 25°F (1991 to 2020)[1]. Modeled value at the city center: 23.2°F[1].

Share of the city's land area by ZIP code zone: zone 9a 94%, zone 8b 6%[15].

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

Zone by ZIP code
ZIP code Zone Coldest night range
78023[15] 8b 15 to 20°F
78223[15] 9a 20 to 25°F
78221[15] 9a 20 to 25°F
78258[15] 9a 20 to 25°F
78264[15] 9a 20 to 25°F
78251[15] 9a 20 to 25°F
78224[15] 9a 20 to 25°F
78247[15] 9a 20 to 25°F
78259[15] 9a 20 to 25°F
78249[15] 9a 20 to 25°F
78216[15] 9a 20 to 25°F
78219[15] 9a 20 to 25°F
78222[15] 9a 20 to 25°F
78227[15] 9a 20 to 25°F
78257[15] 9a 20 to 25°F
78228[15] 9a 20 to 25°F
78218[15] 9a 20 to 25°F
78073[15] 9a 20 to 25°F
78211[15] 9a 20 to 25°F
78217[15] 9a 20 to 25°F
78240[15] 9a 20 to 25°F
78230[15] 9a 20 to 25°F
78250[15] 9a 20 to 25°F
78233[15] 9a 20 to 25°F
78232[15] 9a 20 to 25°F
78214[15] 9a 20 to 25°F
78112[15] 9a 20 to 25°F
78242[15] 9a 20 to 25°F
78238[15] 9a 20 to 25°F
78210[15] 9a 20 to 25°F

Questions people ask

What growing zone is San Antonio?
The 2023 USDA map puts the center of San Antonio in zone 9a[1]. By land area, 94% of the city is in ZIP code areas rated 9a and 6% in areas rated 8b[15].
When is the last frost in San Antonio?
The median last spring frost is February 26, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after March 17[2].
When is the first frost in San Antonio?
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 7[3].
When to plant tomatoes in San Antonio?
CSU Extension typically plants tomatoes 2 or more weeks after the average last spring frost, which gives March 12 as the earliest start[10]. CSU's guide was written for Colorado[10].
How long is the growing season in San Antonio?
The growing season is at least 277 days in half of years[4]. It is at least 247 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of San Antonio, Texas in zone 9a. Zone 9a means an average annual extreme minimum temperature of 20°F to 25°F over 1991 to 2020. The map's modeled value at the city center is 23.2°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 29, in half of years after February 26, and in 1 of 10 years after March 17 (NOAA 1991 to 2020 normals). The median last frost date is February 26. 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 7, in half of years before November 28, and in 9 of 10 years before December 22 (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 247 days in 9 of 10 years, at least 277 days in half of years, and at least 311 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the San Antonio International Airport weather station (USW00012921), 6.1 miles from the center of San Antonio at 789 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 February 9 and the median first fall date is December 13. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 99.9% of years from 1991 to 2020, and 28°F or colder in 95.9% 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. San Antonio, Texas overlaps 40 ZIP code areas. By land area, 94% lies in ZIP code areas rated zone 9a, 6% lies in ZIP code areas rated zone 8b. 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.