Frost Dates for San Juan, TX 78589
Last spring frost December 27 · First fall frost January 22 · 26 frost-free days · USDA Zone 10a
Frost probability for 78589
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | February 14 | December 27 | — |
| Fall (first frost) | December 13 | January 22 | — |
Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (8.9 km away); the 50% date is the median year.
Month by month in San Juan
| Month | What to do |
|---|---|
| January | Plant cool-season crops: lettuce, spinach, broccoli, peas, and carrots. |
| February | Direct sow brassicas and root vegetables. Start warm-season seedlings indoors. |
| March | Transplant warm-season crops outdoors. Sow beans, cucumbers, and squash. |
| April | Main warm-season planting window. Direct sow melons and sweet corn. |
| May | Succession plant lettuce. Keep beds irrigated as temperatures climb. |
| June | Monitor for heat stress. Harvest zucchini and cucumbers frequently. |
| July | Harvest regularly to encourage continued production. Watch for pests. |
| August | Start fall cool-season crops: broccoli, kale, beets, and carrots. |
| September | Plant fall lettuce, spinach, arugula, and radishes. |
| October | Harvest mature crops. Direct sow cold-tolerant greens. |
| November | Plant garlic and onion sets. Harvest cool-season crops through the month. |
| December | Plant cool-season crops for winter harvest. Plan next year's garden. |
What grows in a 26-day season
Frequently Asked Questions
What is the last frost date for San Juan, TX (ZIP 78589)?
The median last spring frost date for San Juan, TX (ZIP code 78589) is around December 27. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.
What is the first fall frost date in San Juan, TX?
The median first fall frost date for San Juan, TX is around January 22. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.
How long is the growing season in San Juan, TX?
The frost-free growing season in San Juan is about 26 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.
What USDA hardiness zone is San Juan, TX?
Based on frost date patterns, San Juan falls approximately in 10a. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.
When should I start tomatoes indoors in San Juan, TX?
Start tomato seeds indoors 6–8 weeks before your last frost date (around December 27). For San Juan, that's roughly November 1 to November 15. Transplant outdoors 1–2 weeks after your last frost.
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