When to plant broccoli in Billings, Montana

April 12 – April 26

Transplant outdoors · typical Billings year

Climate basis: NOAA station Billings Wtp, MT (USC00240802), 13 mi (21 km) from downtown Billings (ZCTA 59101 centroid), elevation 3097 ft, on the 1991–2020 climate normals. Transplant broccoli outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (May 10). One year in ten still freezes after May 24.

Last spring freezeMay 101-in-10 after May 24

First fall freezeOctober 11-in-10 before Sep 19

Frost-free season≈ 142 daysmedian at 32°F

Hard freeze, 28°Apr 27 – Oct 12kills even hardy greens

USDA zone5a-20 to -15°F winter low — not frost timing

The Billings year

Start seeds indoorsMar 1 – Mar 15

Transplant outdoorsApr 12 – Apr 26

Fall plantingAug 6 – Sep 3

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 24

Broccoli in Billings · freeze context from Billings Wtp, MT, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 1 – Mar 15

Sow 4–6 weeks before the set-out window opens (UNH 4–6 weeks; Missouri G6570 6–8 weeks). Anchored to the median last spring freeze (May 10). University of New Hampshire Extension · University of Missouri Extension

Transplant outdoors

Apr 12 – Apr 26

UNH: set out 2–4 weeks before the last frost; Purdue's hardy class allows 4–6 weeks before. The later UNH range is used. Anchored to the median last spring freeze (May 10). University of New Hampshire Extension · Purdue University Extension

Fall planting

Aug 6 – Sep 3

Purdue Table 2: plant fall broccoli at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Oct 1). Purdue University Extension

Variety assumption: Assumes an average heading variety (about 60–70 days from transplant).

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 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.

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