USDA Hardiness Zone 9b
Frost Dates for 77480 — Sweeny, Texas
NOAA 1991–2020 normals from Angleton Brazoria Airport, TX (25 ft), 16 miles east.
Updated
In Sweeny, the last spring frost (32°F) is around February 13 in half of years and has passed by March 17 in nine years out of ten. The first fall frost comes around December 8, as early as November 18 one year in ten, leaving a typical freeze-free season of 301 days (NOAA, Angleton Brazoria Airport, TX).
- Last spring frost
- February 13
- First fall frost
- December 8
- Growing season
- 301 days
- Hardiness zone
- 9b
50% probability
50% probability
freeze-free, 50%
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 0%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
0 of 21 observed
NOAA normal
Frost risk by date in Sweeny
Half of springs at Angleton Brazoria Airport, TX see their last 32°F night by February 13; only one in ten is past it by January 10, and one in ten still has one after March 17. Planting tender crops after February 26 leaves a 30% risk of a frost on them, after March 5 20%, and after March 17 10%. The 32 days between the even-odds date and the one-in-ten date is wider than at 94% 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 8 in half of years, as early as November 18 one year in ten, and holds off past January 12 one year in ten. A hard freeze of 28°F follows 24 days later, around January 1; in spring the one-in-ten date for 28°F is March 3, 14 days before the 32°F one. The freeze-free season lasts 301 days in a typical year, longer than at 88% of the 339 Texas stations; it reaches 341 days one year in ten and falls short of 262 one year in ten. On average 10 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 17 days longer, to about March 2, and return around November 25. A 24°F night is unusual: 37% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jan 31 | Feb 14 | Feb 21 | Feb 26 | Mar 2 | Mar 9 | Mar 14 | Mar 22 | Mar 31 |
| 32°F98% of yrs | Jan 10 | Jan 23 | Jan 31 | Feb 5 | Feb 13 | Feb 20 | Feb 26 | Mar 5 | Mar 17 |
| 28°F78% of yrs | Dec 23 | Jan 2 | Jan 11 | Jan 18 | Jan 26 | Feb 1 | Feb 9 | Feb 19 | Mar 3 |
| 24°F37% of yrs | too rare for a date | ||||||||
| 20°F7% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 5 | Nov 12 | Nov 16 | Nov 20 | Nov 25 | Nov 29 | Dec 3 | Dec 7 | Dec 16 |
| 32°F98% of yrs | Nov 18 | Nov 25 | Nov 30 | Dec 4 | Dec 8 | Dec 15 | Dec 23 | Jan 1 | Jan 12 |
| 28°F78% of yrs | Dec 3 | Dec 11 | Dec 18 | Dec 25 | Jan 1 | Jan 5 | Jan 11 | Jan 21 | Feb 5 |
| 24°F37% of yrs | too rare for a date | ||||||||
| 20°F7% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Angleton Brazoria 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 77480 →Compare Sweeny with another place →
Weather by month in Sweeny
August is the warmest month at Angleton Brazoria Airport, TX, averaging 93°F by day and 75°F at night; January is the coldest at 65°F and 45°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 53% of years and March still brings one in 25% of years.
Warmth for growing adds up to 7,691 growing degree days a year (base 50°F), more than at 82% of the 351 Texas stations. 43% of them (3,319) have built up by the end of June, and August adds the most, 1,051. Precipitation totals 45.8 inches a year, most in September (6.0") and least in February (2.2"); May to September bring 48% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 65 | 45 | 4.2 | 76% | 4 | 209 |
| Feb | 69 | 49 | 2.2 | 53% | 2 | 270 |
| Mar | 74 | 54 | 3.1 | 25% | 1 | 443 |
| Apr | 79 | 60 | 2.4 | 2% | 0 | 594 |
| May | 86 | 68 | 4.3 | 0% | 0 | 839 |
| Jun | 91 | 73 | 3.8 | 0% | 0 | 964 |
| Jul | 93 | 75 | 3.9 | 0% | 0 | 1049 |
| Aug | 93 | 75 | 4.2 | 0% | 0 | 1051 |
| Sep | 89 | 71 | 6.0 | 0% | 0 | 903 |
| Oct | 84 | 62 | 4.4 | 1% | 0 | 704 |
| Nov | 74 | 53 | 3.6 | 30% | 1 | 410 |
| Dec | 67 | 47 | 3.7 | 69% | 3 | 255 |
Monthly normals 1991–2020 at Angleton Brazoria Airport, TX (25 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, Bay City Wtr Wks, TX, 17 miles west of Sweeny, has a last frost 7 days later (February 20), a first frost 5 days earlier (December 3), a season 11 days shorter.
When it snows in Sweeny, Texas
Measurable snow is rare here: only 0 of 21 winters from 1991 to 2020 recorded 0.1 inch or more at Bay City Wtr Wks, TX, 16.7 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 77480
| When | What to do |
|---|---|
| December 5 – December 19 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 19 – January 2 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 16 – January 30 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 13 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 15 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 24 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 8 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 77480 is 16 miles from Angleton Brazoria Airport, TX, which stands at 25 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 77422 (Brazoria). The 2023 USDA Plant Hardiness Zone Map lists ZIP 77480 in zone 9b, the band where the coldest night of the year averaged 25 to 30°F (-3.9 to -1.1°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.