When to plant Onion sets in Wyoming

In spring, from Apr 10 – May 1 in Casper to May 10 – June 10 in Laramie.

In fall, May 1 – June 10.

USDA's earliest safe spring and latest safe fall planting dates, matched to each place's average frost dates.

Onion sets planting dates by place in Wyoming
PlaceSpringFall
CasperApr 10 – May 1Spring-planted
CheyenneApr 10 – May 1Spring-planted
CodyApr 10 – May 1Spring-planted
EvanstonMay 10 – June 10May 1 – June 10
GilletteApr 10 – May 1Spring-planted
Green RiverApr 20 – May 15Spring-planted
JacksonMay 10 – June 10May 1 – June 1
LaramieMay 10 – June 10May 1 – June 1
RivertonApr 10 – May 1Spring-planted
Rock SpringsApr 20 – May 15Spring-planted
SheridanApr 20 – May 15Spring-planted

Planting dates: USDA Home and Garden Bulletin No. 9 (1967), tables 4 and 5. Frost dates: NOAA U.S. Climate Normals 1991–2020. “—” means the place's frost date is outside the table. The full USDA table for onion sets.