When to plant onions in Austin, Texas

February 10 – February 24

Transplant outdoors · typical Austin year

Climate basis: NOAA station Austin 6s, TX (USC00410431), 3 mi (5 km) from downtown Austin (ZCTA 78701 centroid), elevation 570 ft, on the 1991–2020 climate normals. Plant onion sets or transplants from approximately the dates above, anchored to the median last spring 32°F freeze (March 10). One year in ten still freezes after March 31.

Last spring freezeMarch 101-in-10 after Mar 31

First fall freezeNovember 171-in-10 before Nov 1

Frost-free season≈ 252 daysmedian at 32°F

Hard freeze, 28°Feb 28 – Dec 1kills even hardy greens

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

The Austin year

Start seeds indoorsDec 2 – Dec 16

Transplant outdoorsFeb 10 – Feb 24

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Mar 31

Onions in Austin · freeze context from Austin 6s, TX, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Dec 2 – Dec 16

Sow 8–10 weeks (UNH) to 10–12 weeks (Minnesota) before planting out; derived from the −4-week set-out date using the UNH lead time. Anchored to the median last spring freeze (Mar 10). University of New Hampshire Extension · University of Minnesota Extension

Transplant outdoors

Feb 10 – Feb 24

UNH: set out transplants (or sets) 4 weeks before the last frost; Purdue's hardy class allows 4–6 weeks before. The later UNH point is used, with a 14-day span. Anchored to the median last spring freeze (Mar 10). University of New Hampshire Extension · Purdue University Extension

Variety assumption: Assumes storage-type bulb onions (about 100–115 days from sets; Penn State lists 105).

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 (3)

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 Minnesota Extension: Growing onions (accessed 2026-07-24)
"You can also raise your own transplants by starting seed indoors 10 to 12 weeks before planting outside."
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.

Keep exploring

This crop, other cities

Related crops in Austin

Local overview