When to plant winter squash in San Antonio, Texas

March 11 – March 25

Transplant outdoors · typical San Antonio year

Climate basis: NOAA station San Antonio Incarnate Word, TX (USC00417947), 3 mi (5 km) from downtown San Antonio (ZCTA 78205 centroid), elevation 700 ft, on the 1991–2020 climate normals. Transplant winter squash outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (February 25). One year in ten still freezes after March 19.

Last spring freezeFebruary 251-in-10 after Mar 19

First fall freezeNovember 281-in-10 before Nov 7

Frost-free season≈ 277 daysmedian at 32°F

Hard freeze, 28°Feb 5 – Dec 15kills even hardy greens

USDA zone9a20 to 25°F winter low — not frost timing

The San Antonio year

Start seeds indoorsFeb 11 – Feb 18

Transplant outdoorsMar 11 – Mar 25

Direct-sow outdoorsMar 11 – Mar 25

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Mar 19

Winter squash in San Antonio · freeze context from San Antonio Incarnate Word, TX, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Feb 11 – Feb 18

Sow in pots 3–4 weeks before the outdoor window opens (UNH 3–4 weeks; Missouri G6570 3–5 weeks). Anchored to the median last spring freeze (Feb 25). University of New Hampshire Extension · University of Missouri Extension

Transplant outdoors

Mar 11 – Mar 25

UNH: set out 2 weeks after last frost; Purdue very-tender class agrees. Anchored to the median last spring freeze (Feb 25). University of New Hampshire Extension · Purdue University Extension

Direct-sow outdoors

Mar 11 – Mar 25

Purdue: very tender — at least two weeks after the average last frost; Penn State earliest sowing May 15 (+14 days) agrees. Anchored to the median last spring freeze (Feb 25). Purdue University Extension · Penn State Extension (York County Master Gardeners)

Variety assumption: Assumes an average butternut/acorn-type variety (about 90–110 days; Penn State lists 90). Fruit must mature before fall frost.

These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.

This week, not a typical year:

Crop rule sources (4)

University of New Hampshire Extension: Growing Vegetables: When to Plant Your Vegetable Garden [fact sheet] (accessed 2026-07-24)
Per-crop 'time from seed to transplant' and 'safe to set out in garden' relative to last frost.
University of Missouri Extension: Starting Plants Indoors from Seeds (G6570) (accessed 2026-07-24)
Weeks needed to grow vegetable transplants indoors (Table 2).
Purdue University Extension: Indiana Vegetable Planting Calendar (HO-186-W) (accessed 2026-07-24)
Hardiness classes: hardy = plant 4-6 wk before last spring frost; semi-hardy = 2-4 wk before; tender = after average last frost; very tender = at least 2 wk after. Table 2: fall planting at least 4-8 wk before first fall frost.
Penn State Extension (York County Master Gardeners): Vegetable Seed Planting Guide (accessed 2026-07-24)
Earliest/latest sowing dates for a May 1 last-frost / Oct 1 first-frost baseline; offsets derived by date difference from May 1. Also days-to-maturity figures.

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