USDA Hardiness Zone 10a
Frost Dates for 78589 — San Juan, Texas
NOAA 1991–2020 normals from Mcallen, TX (100 ft), 6 miles west.
Updated
Frost is not a yearly event in San Juan: a night at or below 32°F came in 48% of the winters of 1991–2020 at Mcallen, TX, and a 36°F night, cold enough for frost on exposed leaves, in 87%. There is no reliable "last frost date" here; most years have none.
- Winters with a freeze
- 48%
- Winters with 36°F
- 87%
- Coldest month low
- 49°F
- Hardiness zone
- 10a
32°F or below, 1991–2020
frost possible on leaves
average, January
30 to 35°F (-1.1 to 1.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 5%
- Snow per year
- 0.1"
median, 1991–2020
median, 1991–2020
1 of 19 observed
NOAA normal
Frost risk by date in San Juan
At Mcallen, TX, 6 miles west of San Juan, 48% of the winters of 1991–2020 had at least one night at or below 32°F, 16% reached 28°F. Nights of 36°F, enough for frost on exposed leaves, are more common (87% of winters) and, when they come, fall between about December 19 and January 27. January is the month most likely to bring one: a 22% chance in a given year. 11 of the 351 other Texas stations behind this site's ZIP pages freeze in fewer than half of winters too.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F87% of yrs | Dec 20 | Jan 2 | Jan 10 | Jan 18 | Jan 27 | Feb 2 | Feb 9 | Feb 18 | Mar 1 |
| 32°F48% of yrs | too rare for a date | ||||||||
| 28°F16% of yrs | too rare for a date | ||||||||
| 24°F3% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F87% of yrs | Nov 27 | Dec 3 | Dec 8 | Dec 13 | Dec 19 | Dec 25 | Jan 1 | Jan 9 | Jan 26 |
| 32°F48% of yrs | too rare for a date | ||||||||
| 28°F16% of yrs | too rare for a date | ||||||||
| 24°F3% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Mcallen, 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 78589 →Compare San Juan with another place →
Weather by month in San Juan
August is the warmest month at Mcallen, TX, averaging 99°F by day and 77°F at night; January is the coldest at 71°F and 49°F. From March to November the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 13% of years.
Warmth for growing adds up to 9,366 growing degree days a year (base 50°F), more than at 99% of the 351 Texas stations. 45% of them (4,238) have built up by the end of June, and August adds the most, 1,176. Precipitation totals 18.8 inches a year, most in September (3.8") and least in February (0.6"); May to September bring 61% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 71 | 49 | 0.7 | 22% | 1 | 344 |
| Feb | 76 | 53 | 0.6 | 13% | 1 | 422 |
| Mar | 82 | 59 | 1.0 | 0% | 0 | 633 |
| Apr | 87 | 65 | 1.4 | 0% | 0 | 783 |
| May | 92 | 71 | 1.4 | 0% | 0 | 977 |
| Jun | 96 | 76 | 3.1 | 0% | 0 | 1080 |
| Jul | 98 | 77 | 1.6 | 0% | 0 | 1150 |
| Aug | 99 | 77 | 1.5 | 0% | 0 | 1176 |
| Sep | 94 | 73 | 3.8 | 0% | 0 | 1011 |
| Oct | 89 | 66 | 2.0 | 0% | 0 | 860 |
| Nov | 80 | 57 | 1.1 | 1% | 0 | 555 |
| Dec | 73 | 51 | 0.6 | 22% | <1 | 376 |
Monthly normals 1991–2020 at Mcallen, TX (100 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, Mcallen Miller International Airport, TX, 6 miles west of San Juan, has a 32°F night in 29% of winters against 48% here, and a coolest-month low 4°F warmer (53°F).
When it snows in San Juan, Texas
Measurable snow is rare here: only 1 of 19 winters from 1991 to 2020 recorded 0.1 inch or more at Mcallen, TX, 6.1 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 78589 is 6 miles from Mcallen, TX, which stands at 100 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 78577 (Pharr). The 2023 USDA Plant Hardiness Zone Map lists ZIP 78589 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.