FrostList

When to Prevent Frozen Pipes in San Marcos, TX

ON TRACK141 days until first freezing night (32°F)Nov 29

The first freezing night in San Marcos averages November 29 and can arrive as early as November 8 (1991–2020 normals), and the real danger starts when lows drop into the low 20s. Cold deepens quickly here — only about 16 days separate the first frost from that hard freeze.

OUTLOOK

Typical first first freezing night (32°F) near Nov 29; local deadline about Nov 8. The live 10-day outlook loads here.

Local freeze dates for San Marcos

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Nov 8Nov 29Dec 21
28°F (hard freeze)Nov 19Dec 15Jan 13
24°F (severe)Dec 5Jan 2Feb 5

NOAA station: San Marcos · 0.5 mi away · 665 ft elevation.

The reference station for San Marcos is San Marcos (0.5 mi, 665 ft). First freeze there: 32°F by Nov 29, 28°F by Dec 15, 24°F by Jan 2. Year to year the 28°F date has ranged from Nov 19 to Jan 13 — about 55 days apart. Spring's last 32°F freeze clears around Feb 28.

In San Marcos, freezing nights (32°F) typically begin around Nov 29 and the first hard freeze (28°F) follows near Dec 15. That first freezing night has ranged from Nov 8 to Dec 21, roughly a 43-day spread. On the spring side, the last 32°F freeze clears around Feb 28 and as late as Mar 21 — the green light for reopening water and de-winterizing. With almost no snow in a normal year, cold — not plowing — sets the calendar, and it centers on Feb 28.

Your frozen pipes checklist

  1. Disconnect, drain, and store garden hoses, then shut off and drain any interior valves that feed outdoor faucets.
  2. Insulate exposed pipes in the garage, crawl space, and along exterior walls with foam sleeves rated for the pipe size.
    Helpful gear: Foam pipe insulation sleeves — Recommended pick
  3. On nights in the low 20s, let a pencil-thin stream of water drip from the faucet farthest from where the line enters.
  4. Open cabinet doors under kitchen and bathroom sinks on outside walls so household heat reaches the plumbing.
  5. Add self-regulating heat cable to the runs most likely to freeze, such as a pipe in an unheated garage.
    Helpful gear: Self-regulating heat cable — Recommended pick
  6. Cap outdoor faucets with insulated covers once the hoses are off.
    Helpful gear: Outdoor faucet covers — Recommended pick
  7. Know where your main shutoff is and confirm it turns; a fast shutoff limits water damage if a line lets go.
  8. If you travel, keep the thermostat at 55°F or higher and ask someone to check the house during a cold snap.
    Helpful gear: Wi-Fi water leak sensor — Recommended pick

What to have on hand

Foam pipe insulation sleeves
Split foam tubing for exposed pipes in crawl spaces and garages.
Recommended pick
Self-regulating heat cable
Thermostatic cable that warms vulnerable runs only when it is cold.
Recommended pick
Outdoor faucet covers
Insulated caps for hose bibs once the hoses come off.
Recommended pick
Wi-Fi water leak sensor
Puck that pings your phone the moment it senses water.
Recommended pick

What this means locally

Compared with nearby cities, San Marcos's first-freeze date near Nov 29 sits later than New Braunfels (Nov 18) and later than Austin (Nov 17). Texas's deadlines span Oct 16 to Dec 13 statewide — one date for all of Texas would be off by weeks for San Marcos. Once you know San Marcos's freeze date, use it to shut down your sprinklers and check your car battery too.

Other winter jobs in San Marcos

Every task below is dated to San Marcos's own freeze and snow normals.

Sprinklers → Dec 5Car battery → Dec 15Sump pump → Feb 28RV → Dec 5Boat → Dec 8Motorcycle → Nov 29

See the full San Marcos winter checklist, in order →

Frequently asked questions

At what temperature do pipes freeze?
Pipes generally come under risk when the temperature outside falls to about 20°F, the threshold many guides use for taking action. Pipes in unheated or exterior-wall spaces freeze sooner than well-insulated interior runs. Wind and poor insulation lower the effective temperature, so a windy night in the mid-20s can be as risky as a still night in the low 20s.
Should I drip my faucets tonight in San Marcos?
If the overnight low is forecast at or below about 20°F, letting a thin stream run from the faucet farthest along the line is a low-cost precaution. Moving water is slower to freeze and relieves pressure. Check tonight's low against the live outlook above; freezing nights here typically begin around Nov 29.
How long does it take for pipes to freeze?
There is no fixed clock; it depends on pipe location, insulation, and how far below freezing the air drops. An exposed pipe in a windy, unheated space can freeze in a matter of hours during a hard cold snap, while a protected interior pipe may never reach freezing. The colder and windier it is, the faster it happens.
Which pipes freeze first?
The most exposed pipes freeze first: outdoor hose bibs, and lines in unheated garages, crawl spaces, attics, and along exterior walls. Pipes under sinks on outside walls are common trouble spots. That is why disconnecting hoses and opening cabinet doors on cold nights are two of the highest-value steps.
Does homeowners insurance cover burst pipes?
Sudden, accidental water damage from a frozen pipe is often covered, but insurers may deny a claim if the home was left unheated or the damage is judged to be from neglect. Coverage varies by policy. Keeping the heat on and taking reasonable precautions helps protect both your home and your claim.
What temperature should I keep my house if I'm away?
A common recommendation is to keep the thermostat no lower than 55°F while you are away so interior walls stay warm enough to protect the plumbing. Leaving cabinet doors open and having someone check the house during a cold snap adds a margin of safety, especially for pipes on exterior walls.

Data: NOAA 1991–2020 normals via San Marcos, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.