USDA Hardiness Zone 10a
Frost Dates for 78573 — Alton, Texas
NOAA 1991–2020 normals from La Joya, TX (213 ft), 9 miles southwest.
Updated
A freeze (32°F) reaches Alton in 79% of winters. When it does, the first fall frost comes around December 28 and the last spring frost around January 23; after February 27 the chance of another is under 8%.
- Last spring frost
- January 23
- First fall frost
- December 28
- Winters with a freeze
- 79%
- Hardiness zone
- 10a
50%, in freezing years
50%, in freezing years
32°F or below, 1991–2020
30 to 35°F (-1.1 to 1.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 7%
- Snow per year
- 0.2"
median, 1991–2020
median, 1991–2020
1 of 15 observed
NOAA normal
Frost risk by date in Alton
In the 79% of winters that bring a 32°F night, half of springs at La Joya, TX see their last 32°F night by January 23; only one in ten is past it by December 22, and one in ten still has one after February 27. Counting the winters with no freeze at all, the risk of a 32°F night after February 27 is under 8% and after January 23 39%. The 35 days between the even-odds date and the one-in-ten date is wider than at 97% 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 December 28 in half of years, as early as December 2 one year in ten, and holds off past February 1 one year in ten. A hard freeze of 28°F is less common: it came in 39% of winters. The freeze-free season lasts 340 days in a typical year, longer than at 98% of the 339 Texas stations; it reaches 365 days one year in ten and falls short of 305 one year in ten. On average 2 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 19 days longer, to about February 11, and return around December 7. A 24°F night is unusual: 11% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F99% of yrs | Jan 9 | Jan 21 | Jan 29 | Feb 4 | Feb 11 | Feb 17 | Feb 26 | Mar 3 | Mar 11 |
| 32°F79% of yrs | Dec 22 | Jan 1 | Jan 8 | Jan 15 | Jan 23 | Jan 31 | Feb 4 | Feb 14 | Feb 27 |
| 28°F39% of yrs | too rare for a date | ||||||||
| 24°F11% of yrs | too rare for a date | ||||||||
| 20°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F99% of yrs | Nov 18 | Nov 25 | Nov 29 | Dec 3 | Dec 7 | Dec 13 | Dec 20 | Dec 28 | Jan 7 |
| 32°F79% of yrs | Dec 2 | Dec 8 | Dec 15 | Dec 22 | Dec 28 | Jan 1 | Jan 6 | Jan 15 | Feb 1 |
| 28°F39% of yrs | too rare for a date | ||||||||
| 24°F11% of yrs | too rare for a date | ||||||||
| 20°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at La Joya, 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 78573 →Compare Alton with another place →
Weather by month in Alton
August is the warmest month at La Joya, TX, averaging 97°F by day and 75°F at night; January is the coldest at 69°F and 47°F. From March to November the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 23% of years.
Warmth for growing adds up to 8,639 growing degree days a year (base 50°F), more than at 94% of the 351 Texas stations. 45% of them (3,894) have built up by the end of June, and August adds the most, 1,113. Precipitation totals 20.3 inches a year, most in September (3.5") and least in January (0.8"); May to September bring 53% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 69 | 47 | 0.8 | 49% | 1 | 283 |
| Feb | 74 | 51 | 0.9 | 23% | 1 | 368 |
| Mar | 79 | 57 | 1.4 | 7% | 0 | 572 |
| Apr | 85 | 63 | 1.7 | 0% | 0 | 715 |
| May | 90 | 70 | 1.9 | 0% | 0 | 925 |
| Jun | 95 | 74 | 2.0 | 0% | 0 | 1032 |
| Jul | 95 | 75 | 2.2 | 0% | 0 | 1087 |
| Aug | 97 | 75 | 1.2 | 0% | 0 | 1113 |
| Sep | 92 | 71 | 3.5 | 0% | 0 | 948 |
| Oct | 87 | 64 | 2.2 | 0% | 0 | 777 |
| Nov | 78 | 55 | 1.1 | 6% | 0 | 504 |
| Dec | 71 | 48 | 1.4 | 42% | 1 | 317 |
Monthly normals 1991–2020 at La Joya, TX (213 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, Edinburg, TX, 9 miles southeast of Alton, has a 32°F night in 40% of winters against 79% here, and a coolest-month low 2°F warmer (49°F).
When it snows in Alton, Texas
Measurable snow is rare here: only 1 of 15 winters from 1991 to 2020 recorded 0.1 inch or more at La Joya, TX, 8.6 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 78573 is 9 miles from La Joya, TX, which stands at 213 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 78572 (Mission). The 2023 USDA Plant Hardiness Zone Map lists ZIP 78573 in zone 10a, the band where the coldest night of the year averaged 30 to 35°F (-1.1 to 1.7°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.