When to plant onions in Syracuse, New York

April 1 – April 15

Transplant outdoors · typical Syracuse year

Climate basis: NOAA station Syracuse Hancock INTL AP, NY (USW00014771), 5 mi (8 km) from downtown Syracuse (ZCTA 13202 centroid), elevation 413 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 (April 29). One year in ten still freezes after May 13.

Last spring freezeApril 291-in-10 after May 13

First fall freezeOctober 191-in-10 before Oct 2

Frost-free season≈ 173 daysmedian at 32°F

Hard freeze, 28°Apr 16 – Nov 2kills even hardy greens

USDA zone6a-10 to -5°F winter low — not frost timing

The Syracuse year

Start seeds indoorsJan 21 – Feb 4

Transplant outdoorsApr 1 – Apr 15

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 13

Onions in Syracuse · freeze context from Syracuse Hancock INTL AP, NY, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Jan 21 – Feb 4

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 (Apr 29). University of New Hampshire Extension · University of Minnesota Extension

Transplant outdoors

Apr 1 – Apr 15

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 (Apr 29). 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.

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