USDA Hardiness Zone 9a
Frost Dates for 78617 — Del Valle, Texas
NOAA 1991–2020 normals from Austin Bergstrom Airport, TX (480 ft), 4 miles west.
Updated
In Del Valle, the last spring frost (32°F) is around March 12 in half of years and has passed by April 2 in nine years out of ten. The first fall frost comes around November 16, as early as November 1 one year in ten, leaving a typical freeze-free season of 252 days (NOAA, Austin Bergstrom Airport, TX).
- Last spring frost
- March 12
- First fall frost
- November 16
- Growing season
- 252 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
- 27%
- Snow per year
- 0.2"
median, 1991–2020
median, 1991–2020
6 of 22 observed
NOAA normal
Frost risk by date in Del Valle
Half of springs at Austin Bergstrom Airport, TX see their last 32°F night by March 12; only one in ten is past it by February 20, and one in ten still has one after April 2. Planting tender crops after March 21 leaves a 30% risk of a frost on them, after March 28 20%, and after April 2 10%. The 21 days between the even-odds date and the one-in-ten date is wider than at 50% of the 339 Texas stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.
In fall the first 32°F night comes by November 16 in half of years, as early as November 1 one year in ten, and holds off past December 5 one year in ten. A hard freeze of 28°F follows 15 days later, around December 1; in spring the one-in-ten date for 28°F is March 19, 14 days before the 32°F one. The freeze-free season lasts 252 days in a typical year, longer than at 55% of the 339 Texas stations; it reaches 279 days one year in ten and falls short of 223 one year in ten. On average 33 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 15 days longer, to about March 27, and return around November 7. Nights of 24°F, cold enough to damage hardier plants, come in 97% of winters and 16°F in 26%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 4 | Mar 12 | Mar 17 | Mar 22 | Mar 27 | Mar 31 | Apr 4 | Apr 8 | Apr 16 |
| 32°F | Feb 20 | Feb 27 | Mar 3 | Mar 8 | Mar 12 | Mar 16 | Mar 21 | Mar 28 | Apr 2 |
| 28°F | Jan 28 | Feb 6 | Feb 16 | Feb 23 | Feb 27 | Mar 3 | Mar 7 | Mar 12 | Mar 19 |
| 24°F97% of yrs | Jan 3 | Jan 14 | Jan 24 | Jan 30 | Feb 5 | Feb 14 | Feb 22 | Mar 2 | Mar 8 |
| 20°F68% of yrs | Dec 24 | Jan 1 | Jan 6 | Jan 12 | Jan 20 | Jan 26 | Feb 1 | Feb 10 | Feb 23 |
| 16°F26% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 25 | Oct 31 | Nov 2 | Nov 5 | Nov 7 | Nov 11 | Nov 13 | Nov 17 | Nov 25 |
| 32°F | Nov 1 | Nov 6 | Nov 10 | Nov 13 | Nov 16 | Nov 21 | Nov 26 | Nov 30 | Dec 5 |
| 28°F | Nov 10 | Nov 16 | Nov 22 | Nov 27 | Dec 1 | Dec 4 | Dec 8 | Dec 14 | Dec 25 |
| 24°F97% of yrs | Nov 23 | Dec 1 | Dec 5 | Dec 10 | Dec 17 | Dec 24 | Dec 30 | Jan 5 | Jan 15 |
| 20°F68% of yrs | Dec 7 | Dec 15 | Dec 23 | Dec 29 | Jan 1 | Jan 5 | Jan 11 | Jan 19 | Feb 2 |
| 16°F26% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Austin Bergstrom 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 78617 →Compare Del Valle with another place →
Weather by month in Del Valle
August is the warmest month at Austin Bergstrom Airport, TX, averaging 97°F by day and 73°F at night; January is the coldest at 63°F and 38°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 71% of years and April still brings one in 13% of years.
Warmth for growing adds up to 7,053 growing degree days a year (base 50°F), more than at 69% of the 351 Texas stations. 42% of them (2,967) have built up by the end of June, and August adds the most, 1,079. Precipitation totals 35.7 inches a year, most in May (5.0") and least in February (1.9"); May to September bring 45% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 63 | 38 | 2.8 | 100% | 11 | 115 |
| Feb | 66 | 42 | 1.9 | 92% | 7 | 177 |
| Mar | 73 | 49 | 2.9 | 71% | 2 | 359 |
| Apr | 80 | 56 | 2.4 | 13% | <1 | 544 |
| May | 87 | 65 | 5.0 | 0% | 0 | 806 |
| Jun | 93 | 72 | 3.4 | 0% | 0 | 967 |
| Jul | 96 | 73 | 2.2 | 0% | 0 | 1071 |
| Aug | 97 | 73 | 2.5 | 0% | 0 | 1079 |
| Sep | 91 | 67 | 3.0 | 0% | 0 | 871 |
| Oct | 83 | 57 | 4.3 | 7% | <1 | 616 |
| Nov | 72 | 47 | 2.7 | 78% | 3 | 304 |
| Dec | 64 | 40 | 2.6 | 98% | 10 | 144 |
Monthly normals 1991–2020 at Austin Bergstrom Airport, TX (480 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, Austin 6S, TX, 8 miles northwest of Del Valle, has a last frost 2 days earlier (March 10), a first frost 1 day later (November 17).
When it snows in Del Valle, Texas
Measurable snow is rare here: only 6 of 22 winters from 1991 to 2020 recorded 0.1 inch or more at Austin Bergstrom Airport, TX, 3.5 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 78617
| When | What to do |
|---|---|
| January 1 – January 15 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 15 – January 29 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 12 – February 26 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 12 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 24 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 2 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 16 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 78617 is 4 miles from Austin Bergstrom Airport, TX, which stands at 480 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 78610 (Buda). The 2023 USDA Plant Hardiness Zone Map lists ZIP 78617 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.