Frost dates for ZIP 78666 (San Marcos, TX)
Average last spring and first fall frost dates with 10%, 50% and 90% odds, from NOAA's 1991–2020 climate normals for the nearest weather station, San Marcos, TX (2 miles away).
- Average last spring frostFeb 2850% chance of a 32°F freeze after this date
- Average first fall frostNov 2950% chance of a 32°F freeze by this date
- Growing season (frost-free)273 daysmedian, 32°F threshold
- USDA hardiness zone9a20 to 25°F avg. coldest night
Get The Dial for 78666 (San Marcos)
Frost and freeze alerts from the NWS forecast for 78666, the spring soil-temperature heads-up for pre-emergent, and a short weekly yard-timing email.
Free. One weekly email plus alerts when your ZIP has a frost or a soil-temperature change worth acting on. After you submit, Kit (our email provider) sends a confirmation email: check your email and click the link to confirm. You aren't subscribed until you do. We collect only your email address and ZIP, sent to Kit to deliver The Dial. Unsubscribe anytime.
This week in your yard
As of Oct 17, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Pre-emergent
Soil is 77°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent (annual bluegrass, winter weeds): not yet. Apply as soil cools toward 70°F (typically September to early October).
Fertilizer window
Lawn region: South Central plains. Timing only; always follow the product label.
- Bermudagrass (warm-season): Spring: Several weeks after the lawn is fully green (April–May) (about Apr 15 here, using green-up about 3–4 weeks after your average last frost); Summer: Every 4–6 weeks through mid-August (heaviest feeder of the group); Late: Light, low-nitrogen/high-potassium feeding about 4 weeks before first frost, or skip. Avoid: Heavy late-fall nitrogen (linked to spring dead spot).
- Tall fescue (cool-season): Early fall: September (main feeding); Late fall: November, while still green; Late winter: Optional light feeding February–March. Avoid: Feeding after mid-spring and through summer in the transition zone (stress and brown patch).
Plant now
- Lettuce: fall sowing Sep 20–Oct 18
- Lettuce: fall transplant Oct 4–25
- Spinach: fall sowing Oct 4–25
- Bok choy / Asian greens: fall sowing Oct 4–18
- Arugula: fall sowing Oct 4–Nov 1
- Mustard greens: fall sowing Oct 4–18
- Cilantro: fall sowing Oct 4–18
- Dill: fall sowing Oct 4–18
- Strawberry (plants): fall transplant Sep 20–Oct 18
Coming up in the next 3 weeks
Prune now
No frost-timed pruning windows are open this week.
Your average first frost is Nov 29: skip heavy pruning in the 6–8 weeks before it, because new growth may not harden off in time.
Spring-flowering shrubs are pruned right after their flowers fade, not by date. See the pruning guide.
Last spring frost odds
| Chance of a 32°F freeze after this date | Date |
|---|---|
| 90% (early: most years still freeze after this) | Feb 1 |
| 50% (the "average" last frost) | Feb 28 |
| 10% (cautious: only 1 year in 10 freezes later) | Mar 21 |
Most gardeners plant frost-tender crops (tomatoes, peppers, basil) after the 50% date, and closer to the 10% date for less risk.
First fall frost odds
| Chance the first 32°F freeze has happened by this date | Date |
|---|---|
| 10% (early: 1 year in 10 freezes this soon) | Nov 8 |
| 50% (the "average" first frost) | Nov 29 |
| 90% (late: most years have frozen by now) | Dec 21 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Mar 14 | Nov 16 |
| 32°F (freeze) | Feb 28 | Nov 29 |
| 28°F (hard freeze) | Feb 13 | Dec 15 |
n/a means NOAA did not publish a date at that threshold for this station (usually because it rarely gets that cold).
Vegetable planting calendar for 78666
Dates count from your average last spring frost (Feb 28) and first fall frost (Nov 29). Half of years have a frost after the spring date, so give tender crops (tomatoes, peppers, squash) some slack.
| Crop | Start indoors | Spring planting | Fall planting |
|---|---|---|---|
| Tomato | Jan 3–17 | Mar 7–21 (transplant) | Aug 2–30 (transplant) |
| Pepper (sweet and hot) | Dec 20–Jan 3 | Mar 14–28 (transplant) | Aug 9–30 (transplant) |
| Eggplant | Dec 20–Jan 3 | Mar 14–28 (transplant) | Aug 9–30 (transplant) |
| Tomatillo | Jan 3–17 | Mar 7–21 (transplant) | – |
| Lettuce | Jan 3–17 | Feb 7–28 (transplant) Jan 31–Mar 14 (sow outdoors) | Oct 4–25 (transplant) Sep 20–Oct 18 (sowing) |
| Spinach | – | Jan 17–Feb 7 (sow outdoors) | Oct 4–25 (sowing) |
| Kale | Jan 3–17 | Jan 31–Feb 14 (transplant) Jan 31–Feb 14 (sow outdoors) | Sep 6–Oct 4 (transplant) Aug 23–Sep 20 (sowing) |
| Collards | Jan 3–17 | Jan 31–Feb 28 (transplant) Jan 31–Feb 28 (sow outdoors) | Sep 6–Oct 4 (transplant) Aug 23–Sep 20 (sowing) |
| Broccoli | Dec 20–Jan 3 | Jan 31–Feb 14 (transplant) | Aug 23–Sep 20 (transplant) |
| Cabbage | Dec 20–Jan 3 | Jan 31–Feb 14 (transplant) | Aug 23–Sep 20 (transplant) |
| Cauliflower | Dec 20–Jan 3 | Feb 14–28 (transplant) | Aug 23–Sep 20 (transplant) |
| Brussels sprouts | Dec 6–20 | Jan 31–Feb 14 (transplant) | Aug 9–30 (transplant) |
| Kohlrabi | Jan 3–17 | Jan 31–Feb 14 (transplant) Jan 31–Feb 14 (sow outdoors) | Sep 20–Oct 4 (sowing) |
| Bok choy / Asian greens | – | Jan 31–Feb 14 (sow outdoors) | Oct 4–18 (sowing) |
| Arugula | – | Jan 31–Feb 28 (sow outdoors) | Oct 4–Nov 1 (sowing) |
| Mustard greens | – | Jan 31–Feb 21 (sow outdoors) | Oct 4–18 (sowing) |
| Swiss chard | Jan 17–31 | Feb 14–Mar 7 (transplant) Feb 14–Mar 14 (sow outdoors) | Sep 20–Oct 4 (sowing) |
| Beet | – | Jan 31–Feb 28 (sow outdoors) | Sep 20–Oct 4 (sowing) |
| Carrot | – | Feb 7–Mar 7 (sow outdoors) | Sep 6–20 (sowing) |
| Radish | – | Jan 24–Mar 7 (sow outdoors) | Oct 18–Nov 1 (sowing) |
| Turnip | – | Jan 31–Feb 21 (sow outdoors) | Sep 20–Oct 4 (sowing) |
| Parsnip | – | Feb 7–28 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Jan 3–31 (sow outdoors) | Sep 6–20 (sowing) |
| Onion (bulbing) | Dec 6–20 | Jan 17–31 (transplant) | – |
| Green onion / scallion | – | Jan 17–Feb 14 (sow outdoors) | Sep 20–Oct 4 (sowing) |
| Leek | Dec 6–20 | Jan 31–Feb 14 (transplant) | – |
| Garlic | – | – | Oct 18–Nov 15 (sowing) |
| Shallot | – | Jan 17–31 (transplant) | Oct 18–Nov 15 (sowing) |
| Potato | – | Jan 31–Feb 14 (transplant) | Aug 9–23 (transplant) |
| Sweet potato | – | Mar 21–Apr 4 (transplant) | – |
| Sweet corn | – | Mar 7–21 (sow outdoors) | – |
| Bean, bush (snap) | – | Mar 7–21 (sow outdoors) | Sep 6–20 (sowing) |
| Bean, pole | – | Mar 7–21 (sow outdoors) | – |
| Lima bean | – | Mar 14–28 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Mar 21–Apr 11 (sow outdoors) | – |
| Cucumber | Jan 31–Feb 7 | Mar 7–21 (transplant) Mar 7–21 (sow outdoors) | Sep 6–20 (sowing) |
| Summer squash / zucchini | Jan 31–Feb 7 | Mar 7–21 (transplant) Mar 7–21 (sow outdoors) | Sep 6–20 (sowing) |
| Winter squash | Jan 31–Feb 7 | Mar 7–21 (transplant) Mar 7–21 (sow outdoors) | – |
| Pumpkin | – | Mar 7–21 (sow outdoors) | – |
| Watermelon | Jan 31–Feb 7 | Mar 14–28 (transplant) Mar 14–28 (sow outdoors) | – |
| Cantaloupe / muskmelon | Jan 31–Feb 7 | Mar 14–28 (transplant) Mar 14–28 (sow outdoors) | – |
| Okra | Jan 17–31 | Mar 14–28 (transplant) Mar 14–28 (sow outdoors) | – |
| Celery | Dec 6–20 | Mar 7–14 (transplant) | – |
| Basil | Jan 17–31 | Mar 7–21 (transplant) Mar 7–21 (sow outdoors) | – |
| Cilantro | – | Feb 14–Mar 14 (sow outdoors) | Oct 4–18 (sowing) |
| Parsley | Dec 20–Jan 3 | Feb 14–28 (transplant) Feb 7–28 (sow outdoors) | – |
| Dill | – | Feb 28–Mar 14 (sow outdoors) | Oct 4–18 (sowing) |
| Sunflower | – | Feb 28–Mar 14 (sow outdoors) | – |
| Asparagus (crowns) | – | Jan 31–Feb 14 (transplant) | – |
| Rhubarb (crowns) | – | Jan 31–Feb 14 (transplant) | – |
| Strawberry (plants) | – | Jan 31–Feb 14 (transplant) | Sep 20–Oct 18 (transplant) |
Typical ranges from university extension planting calendars, adjusted to your frost dates. Probabilities, not guarantees. Fall windows that would overlap spring planting are left out, as are fall crops of frost-tender plants where the frost-free season is under 210 days.
Plants that do well here
Texas A&M AgriLife trials name plants that handle Texas conditions: the Texas Superstar® list and the low-care roses from AgriLife trials. Plant frost-tender annuals after February 28 here (the average last frost). More on plants for Texas. Not affiliated with Texas A&M AgriLife.
This week in San Marcos
Soil temperature now
2-inch depth
78°F 55°F or warmer
24-hour average · latest 78°F, as of Oct 17, 9:00 PM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Baker Ranch (18 mi), Springs Hill SUD Plant (23 mi), Arnosky Farms (25 mi).
4-inch depth
77°F 55°F or warmer
24-hour average · latest 77°F, as of Oct 17, 9:00 PM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Baker Ranch (18 mi), Springs Hill SUD Plant (23 mi), Arnosky Farms (25 mi).
Fall: Texas A&M AgriLife times fall pre-emergent (for winter weeds such as annual bluegrass) to soil cooling to about 70°F for several days. The 50–55°F band is the spring trigger. Always read and follow the product label.
7-day forecast and frost risk
The latest National Weather Service 7-day forecast and any Frost Advisory or Freeze Warning for 78666 load here. You can also open the NWS forecast for this ZIP.
Where these numbers come from
Station: San Marcos, TX (NOAA GHCN-Daily ID USC00417983), elevation 665 ft, 2.1 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| New Braunfels WFO, TX | 12 mi | Feb 25 | Nov 25 |
| Austin San Antonio, TX | 13 mi | Mar 1 | Nov 26 |
| Canyon Dam, TX | 13 mi | Mar 1 | Dec 1 |
The average last-frost dates of these stations span 7 days, a rough guide to local variation. See data sources & methods.
Frost questions for 78666
When is the last frost in 78666?
The average (50% chance) last spring freeze of 32°F for ZIP 78666 is February 28. For a more cautious planting date, use March 21, when only 1 year in 10 still sees a later freeze.
When is the first frost in 78666?
The average first fall freeze is November 29. In 1 year in 10 it comes by November 8.
What hardiness zone is 78666?
ZIP 78666 is in USDA zone 9a (20 to 25°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 78666 right now?
This page shows the latest 2-inch and 4-inch soil temperature from the nearest public soil station (USDA SCAN, NOAA USCRN or TexMesonet), or a labeled estimate when no station is close, against the 50–55°F spring pre-emergent band.
Nearby ZIP codes
78655 Martindale 78656 San Marcos 78670 Staples 78640 Kyle 78130 New Braunfels 78622 78623 Canyon Lake 78132 Canyon Lake
Other ZIP codes in Hays County
78610 78619 78620 78640 78676 78737 All Hays County frost dates · Texas frost dates
Never miss a frost: get The Dial
Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
Free. One weekly email plus alerts when your ZIP has a frost or a soil-temperature change worth acting on. After you submit, Kit (our email provider) sends a confirmation email: check your email and click the link to confirm. You aren't subscribed until you do. We collect only your email address and ZIP, sent to Kit to deliver The Dial. Unsubscribe anytime.