PlantingWindowThe American Planting Almanac

When to plant radishes in Billings, Montana

April 10 – April 24

Direct-sow 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. Direct-sow radishes 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

Direct-sow outdoorsApr 10 – Apr 24
Fall plantingAug 6 – Sep 3
  • indoors under lights
  • in the garden
  • frost-free season
  • 1-in-10 years still freeze to May 24
Radishes in Billings · freeze context from Billings Wtp, MT, 1991–2020 normals.

Every method, with its sources

Direct-sow outdoors

Apr 10 – Apr 24

Purdue: hardy — 4–6 weeks before the last frost; Penn State's earliest sowing Apr 1 (−30 days) is the later start and is used. Anchored to the median last spring freeze (May 10). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Fall planting

Aug 6 – Sep 3

Purdue Table 2: plant fall radishes 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 a spring type (about 25–35 days; Penn State lists 30).

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 (2)

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