When to plant winter squash in Colorado Springs, Colorado

May 17 – May 31

Transplant outdoors · typical Colorado Springs year

Climate basis: NOAA station Colorado Springs Muni AP, CO (USW00093037), 7 mi (11 km) from downtown Colorado Springs (ZCTA 80903 centroid), elevation 6181 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 (May 3). One year in ten still freezes after May 15.

Last spring freezeMay 31-in-10 after May 15

First fall freezeOctober 81-in-10 before Sep 26

Frost-free season≈ 158 daysmedian at 32°F

Hard freeze, 28°Apr 24 – Oct 16kills even hardy greens

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

The Colorado Springs year

Start seeds indoorsApr 19 – Apr 26

Transplant outdoorsMay 17 – May 31

Direct-sow outdoorsMay 17 – May 31

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 15

Winter squash in Colorado Springs · freeze context from Colorado Springs Muni AP, CO, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Apr 19 – Apr 26

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 (May 3). University of New Hampshire Extension · University of Missouri Extension

Transplant outdoors

May 17 – May 31

UNH: set out 2 weeks after last frost; Purdue very-tender class agrees. Anchored to the median last spring freeze (May 3). University of New Hampshire Extension · Purdue University Extension

Direct-sow outdoors

May 17 – May 31

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 (May 3). 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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