U.S. Frost Dates by Weather Station

NOAA station USC00417983 · Texas

Frost Dates for San Marcos, TX

NOAA weather station San Marcos (USC00417983), Texas · elevation 665 ft (203 m) · hardiness zone 9a*

  • Lower-risk planting dateafter March 21only 1 spring in 10 still has a frost later
  • Typical last frostFebruary 2850% chance of a frost after it
  • Typical first fall frostNovember 2950% chance of a frost before it
  • Frost-free season273 daystypical year, 32°F
  • Hardiness zone9acalculated*

The year at a glance

Frost season at San Marcos, TXSpring: a frost after February 1 in 9 years out of 10, after February 28 in half of the years, after March 21 in 1 year out of 10. Fall: the first frost comes before November 8 in 1 year out of 10, before November 29 in half of the years, before December 21 in 9 years out of 10. Typical frost-free season: 273 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Feb 28First frost ~Nov 29Frost season at San Marcos, TXSpring: a frost after February 1 in 9 years out of 10, after February 28 in half of the years, after March 21 in 1 year out of 10. Fall: the first frost comes before November 8 in 1 year out of 10, before November 29 in half of the years, before December 21 in 9 years out of 10. Typical frost-free season: 273 days.JFMAMJJASONDLast frost ~Feb 28First frost ~Nov 29
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.Today

Frost dates (32°F)

Probability of frost, based on 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)March 21November 8
50% (typical)February 28November 29
90% (likely)February 1December 21
Frost-free season (32°F, 50% chance)
273 days
Hard frost (28°F), last in spring, 50% chance after
February 13
Hard frost (28°F), first in fall, 50% chance before
December 15

The last 15 years (2006–2020 normals)

Typical last frost February 28 (same as the 30-year normal), typical first fall frost December 2 (3 days later). Frost-free season 275 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring at San Marcos: chance of a frost after this dateSpring, chance of a frost after the date: 10% March 21, 20% March 14, 30% March 8, 40% March 4, 50% February 28, 60% February 25, 70% February 20, 80% February 14, 90% February 1. Observed last spring frost in recent years: 2022 March 14, 2023 February 10, 2024 February 18, 2025 February 23, 2026 March 17.Spring: last frostChance of a frost after this date10%50%90%Feb 1Mar 1Apr 1Mar 21Feb 28Feb 12022: March 142023: February 102024: February 182025: February 232026: March 17Fall at San Marcos: chance of a frost before this dateFall, chance of a frost before the date: 10% November 8, 20% November 14, 30% November 19, 40% November 25, 50% November 29, 60% December 2, 70% December 6, 80% December 12, 90% December 21. Observed first fall frost in recent years: 2021 January 2, 2022 December 22, 2023 December 10, 2024 December 11, 2025 December 15.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Jan 1Nov 8Nov 29Dec 212021: January 22022: December 222023: December 102024: December 112025: December 15
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021incomplete recordJanuary 2
2022March 14December 22
2023February 10December 10
2024February 18December 11
2025February 23December 15
2026March 17season not over yet

What these dates mean

The 273 days between the 50% light-frost dates in San Marcos span the interval from February 28, the median spring date, to November 29, the median fall date, and represent the period in which a gardener faces an even chance of a frost later in spring or earlier in fall.

For a cautious spring plan the 10%-chance date, March 21, marks the point when the risk of a light frost later drops to ten percent, while planting on February 1 carries a ninety-percent chance of a frost and is a gamble. In the fall the cautious date is November 8, when there is only a ten-percent chance that a light frost has arrived earlier, whereas counting on crops through December 21 would involve a ninety-percent chance of an early frost.

Hard-frost thresholds are lower, so the median hard-frost dates of February 13 and December 15 indicate conditions that can damage plants more severely than the 32°F light frost.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after March 21" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before November 8" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near San Marcos, TXNumbered nearest stations: 1 — near Canyon Lake, TX — 15 mi; 2 — Luling, TX — 23 mi; 3 — Dripping Springs, TX — 23 mi; 4 — Blanco, TX — 31 mi; 5 — Boerne, TX — 47 mi.25 mi · 40 km1. near Canyon Lake, TX — 15 mi12. Luling, TX — 23 mi23. Dripping Springs, TX — 23 mi34. Blanco, TX — 31 mi45. Boerne, TX — 47 mi5
  1. near Canyon Lake, TX 15 mi (24 km)
  2. Luling, TX 23 mi (36 km)
  3. Dripping Springs, TX 23 mi (38 km)
  4. Blanco, TX 31 mi (51 km)
  5. Boerne, TX 47 mi (76 km)

Sources

* Hardiness zone 9a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 29.8833, -97.9494.