When is the last frost in San Marcos, TX?

The average last spring frost (50% probability of 32°F) in San Marcos is around February 28, based on NOAA/NCEI 1991–2020 normals at the San Marcos, TX station (2.1 mi away). Half of years it falls outside that date, so wait 1–2 weeks past it before setting out frost-tender plants.

When is the first fall frost in San Marcos?

The average first fall frost in San Marcos, TX is around November 29, giving roughly a 273-day frost-free growing season.

What planting zone is San Marcos, TX?

San Marcos is in USDA plant hardiness zone 9a (average annual extreme minimum temperature 20 to 25°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in San Marcos?

In San Marcos, TX the warmest month is August (avg high 96.8°F) and the coldest is January (avg low 38.9°F). It averages about 36.6″ of precipitation a year.

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San Marcos, TX Planting Calendar & Frost Dates

USDA hardiness zone 9a · ZIP 78666 · elevation 203′ · NOAA & USDA data

San Marcos is in USDA hardiness zone 9a (winters can dip to 20 to 25°F), with a growing season of about 273 days between the average last spring frost (February 28) and first fall frost (November 29). The warmest month is August (avg high 96.8°F); the coldest is January (avg low 38.9°F). It averages 36.6″ of precipitation a year. Start cool-season crops several weeks before the last frost; wait until after it for tomatoes, peppers and other tender crops.

Hardiness zone

min temp 20 to 25°F

Last spring frost

February 28

avg (50% prob, 32°F)

First fall frost

November 29

avg (50% prob, 32°F)

Growing season

273 days

frost-free window

Warmest month

August

avg high 96.8°F

Month-by-month typical weather in San Marcos

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at San Marcos, TX (2.1 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)
January	62.3	38.9	50.6	2.4
February	66.6	42.4	54.5	1.7
March	73.1	49.5	61.3	2.8
April	79.8	56.3	68	3.2
May	86.2	64.9	75.5	4.5
June	92.4	71.7	82.1	3.6
July	95.7	73.4	84.5	2.2
August	96.8	73.7	85.2	2.6
September	90.5	68.5	79.5	4
October	82.1	58.1	70.1	4.4
November	71.5	48.3	59.9	2.7
December	63.7	40.8	52.2	2.4

What to plant when in San Marcos

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: January 17 · Transplant out: March 7
Peppers	warm	Start seeds indoors: January 3 · Transplant out: March 14
Cucumbers	warm	Direct sow: March 7
Zucchini / squash	warm	Direct sow: March 7
Bush beans	warm	Direct sow: March 7
Sweet corn	warm	Direct sow: March 7
Basil	warm	Transplant out: March 7
Peas	cool	Sow (spring): January 24 · Sow (fall): October 4
Spinach	cool	Sow (spring): January 17 · Sow (fall): October 4
Lettuce	cool	Sow (spring): January 31 · Sow (fall): October 4
Kale	cool	Transplant (spring): February 7 · Sow (fall): September 20
Broccoli	cool	Transplant (spring): February 14
Carrots	cool	Sow (spring): February 7 · Sow (fall): September 20
Onions	cool	Transplant (spring): January 31
Potatoes	cool	Plant seed potatoes: February 14
Radishes	cool	Sow (spring): January 31 · Sow (fall): October 18

Dates are computed from San Marcos's average frost dates using standard cool-/warm-season timing. They're a starting point — a cold spring, a warm microclimate, or a fast-maturing variety can shift them by a week or two.

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Gear that helps you plant on time

Some links below are Amazon affiliate links (tag theboringthin-20). If you buy through them we may earn a small commission at no extra cost to you — it keeps this almanac free. We only list generic, genuinely-useful categories.

Soil thermometer →Know when the ground is warm enough to sow — the honest signal, not the calendar.Seed-starting trays + dome →Start tomatoes & peppers indoors on the schedule below.Seedling heat mat →Warms the soil for faster, more even germination indoors.Floating row cover / frost cloth →Buys you 4–8°F to beat an early or late frost.Raised garden bed kit →Warms and drains faster in spring than in-ground soil.Garden gloves →Basic kit for transplant day.

Nearby cities in Texas

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Sources & method. Hardiness zone: 2023 USDA Plant Hardiness Zone Map (PRISM Climate Group, Oregon State University). Frost dates & growing season: NOAA/NCEI 1991–2020 U.S. Climate Normals, nearest station with published freeze normals — San Marcos, TX, 2.1 mi (confidence: high). Monthly weather normals: San Marcos, TX, 2.1 mi (confidence: high). ZIP centroid from U.S. Census 2023 ZCTA data. Frost dates are the 50%-probability date — half of years frost occurs outside the stated date. Nothing here is invented; where the nearest station is far, we say so. Last updated 2026-07-22.