USDA Hardiness Zone 9a
Frost Dates for 78216 — San Antonio, Texas
NOAA 1991–2020 normals from San Antonio International Airport, TX (789 ft), 1 miles northeast.
Updated
In San Antonio, the last spring frost (32°F) is around February 26 in half of years and has passed by March 17 in nine years out of ten. The first fall frost comes around November 28, as early as November 7 one year in ten, leaving a typical freeze-free season of 277 days (NOAA, San Antonio International Airport, TX).
- Last spring frost
- February 26
- First fall frost
- November 28
- Growing season
- 277 days
- Hardiness zone
- 9a
50% probability
50% probability
freeze-free, 50%
20 to 25°F (-6.7 to -3.9°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 24%
- Snow per year
- 0.2"
median, 1991–2020
median, 1991–2020
6 of 25 observed
NOAA normal
Frost risk by date in San Antonio
Half of springs at San Antonio International Airport, TX see their last 32°F night by February 26; only one in ten is past it by January 29, and one in ten still has one after March 17. Planting tender crops after March 6 leaves a 30% risk of a frost on them, after March 10 20%, and after March 17 10%. The 19 days between the even-odds date and the one-in-ten date is narrower than at 63% of the 339 Texas stations behind this site's ZIP pages.
In fall the first 32°F night comes by November 28 in half of years, as early as November 7 one year in ten, and holds off past December 22 one year in ten. A hard freeze of 28°F follows 15 days later, around December 13; in spring the one-in-ten date for 28°F is March 7, 10 days before the 32°F one. The freeze-free season lasts 277 days in a typical year, longer than at 76% of the 339 Texas stations; it reaches 311 days one year in ten and falls short of 247 one year in ten. On average 14 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 12 days longer, to about March 10, and return around November 16. Nights of 24°F, cold enough to damage hardier plants, come in 66% of winters and 16°F in 4%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Feb 20 | Feb 27 | Mar 3 | Mar 7 | Mar 10 | Mar 14 | Mar 20 | Mar 25 | Apr 2 |
| 32°F | Jan 29 | Feb 8 | Feb 16 | Feb 21 | Feb 26 | Mar 2 | Mar 6 | Mar 10 | Mar 17 |
| 28°F96% of yrs | Jan 2 | Jan 18 | Jan 26 | Feb 1 | Feb 9 | Feb 15 | Feb 21 | Feb 28 | Mar 7 |
| 24°F66% of yrs | Dec 17 | Dec 30 | Jan 7 | Jan 14 | Jan 22 | Jan 31 | Feb 7 | Feb 15 | Feb 26 |
| 20°F25% of yrs | too rare for a date | ||||||||
| 16°F4% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 1 | Nov 5 | Nov 9 | Nov 13 | Nov 16 | Nov 21 | Nov 24 | Nov 29 | Dec 5 |
| 32°F | Nov 7 | Nov 15 | Nov 20 | Nov 24 | Nov 28 | Dec 1 | Dec 6 | Dec 11 | Dec 22 |
| 28°F96% of yrs | Nov 21 | Nov 28 | Dec 3 | Dec 7 | Dec 13 | Dec 21 | Dec 30 | Jan 6 | Jan 19 |
| 24°F66% of yrs | Dec 2 | Dec 10 | Dec 18 | Dec 26 | Jan 1 | Jan 6 | Jan 13 | Jan 24 | Feb 10 |
| 20°F25% of yrs | too rare for a date | ||||||||
| 16°F4% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at San Antonio International Airport, TX, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 78216 →Compare San Antonio with another place →
Weather by month in San Antonio
August is the warmest month at San Antonio International Airport, TX, averaging 96°F by day and 75°F at night; January is the coldest at 63°F and 41°F. A freezing night is all but certain in January (a 90% chance or more). From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 75% of years and March still brings one in 44% of years.
Warmth for growing adds up to 7,392 growing degree days a year (base 50°F), more than at 77% of the 351 Texas stations. 43% of them (3,144) have built up by the end of June, and August adds the most, 1,099. Precipitation totals 32.5 inches a year, most in May (4.4") and least in February (1.7"); May to September bring 50% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 63 | 41 | 2.0 | 93% | 5 | 143 |
| Feb | 68 | 45 | 1.7 | 75% | 3 | 214 |
| Mar | 74 | 52 | 2.3 | 44% | 1 | 408 |
| Apr | 80 | 58 | 2.4 | 0% | 0 | 581 |
| May | 87 | 66 | 4.4 | 0% | 0 | 822 |
| Jun | 92 | 73 | 3.3 | 0% | 0 | 976 |
| Jul | 95 | 75 | 2.4 | 0% | 0 | 1079 |
| Aug | 96 | 75 | 2.2 | 0% | 0 | 1099 |
| Sep | 90 | 70 | 3.9 | 0% | 0 | 896 |
| Oct | 82 | 60 | 3.8 | 3% | 0 | 661 |
| Nov | 72 | 50 | 2.1 | 56% | 1 | 342 |
| Dec | 65 | 42 | 2.0 | 88% | 4 | 171 |
Monthly normals 1991–2020 at San Antonio International Airport, TX (789 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, San Antonio Incarnate Word, TX, 4 miles south of San Antonio, has a last frost 1 day earlier (February 25), the same first-frost date.
When it snows in San Antonio, Texas
Measurable snow is rare here: only 6 of 25 winters from 1991 to 2020 recorded 0.1 inch or more at San Antonio International Airport, TX, 1.2 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 78216
| When | What to do |
|---|---|
| December 18 – January 1 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 1 – January 15 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 29 – February 12 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 26 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 5 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 14 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 28 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 78216 is 1 mile from San Antonio International Airport, TX, which stands at 789 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 16 other ZIP codes share the station; its figures are presented in full for 78249 (San Antonio). The 2023 USDA Plant Hardiness Zone Map lists ZIP 78216 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.