When to plant winter squash in Salt Lake City, Utah

April 14 – April 28

Transplant outdoors · typical Salt Lake City year

Climate basis: NOAA station Salt Lake Triad Ctr, UT (USC00427606), 1 mi (2 km) from downtown Salt Lake City (ZCTA 84111 centroid), elevation 4280 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 (March 31). One year in ten still freezes after April 19.

Last spring freezeMarch 311-in-10 after Apr 19

First fall freezeNovember 81-in-10 before Oct 23

Frost-free season≈ 224 daysmedian at 32°F

Hard freeze, 28°Mar 8 – Nov 18kills even hardy greens

USDA zone7b5 to 10°F winter low — not frost timing

The Salt Lake City year

Start seeds indoorsMar 17 – Mar 24

Transplant outdoorsApr 14 – Apr 28

Direct-sow outdoorsApr 14 – Apr 28

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

Winter squash in Salt Lake City · freeze context from Salt Lake Triad Ctr, UT, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 17 – Mar 24

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 (Mar 31). University of New Hampshire Extension · University of Missouri Extension

Transplant outdoors

Apr 14 – Apr 28

UNH: set out 2 weeks after last frost; Purdue very-tender class agrees. Anchored to the median last spring freeze (Mar 31). University of New Hampshire Extension · Purdue University Extension

Direct-sow outdoors

Apr 14 – Apr 28

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 (Mar 31). 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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