When to plant Onions in Washington

In spring, from Jan 1 – Feb 1 in Burien to May 1 – 30 in Cheney.

In fall, from May 1 – June 10 in Cheney to Oct 1 – Dec 31 in Woodinville.

Dates are for setting out plants. USDA's earliest safe spring and latest safe fall planting dates, matched to each place's average frost dates.

Onion plants planting dates by place in Washington
PlaceSpringFall
AberdeenFeb 15 – Mar 15Sept 1 – Oct 15
Airway HeightsApr 1 – May 1Spring-planted
AnacortesJan 15 – Feb 15Oct 1 – Dec 31Now
ArlingtonMar 15 – Apr 10Spring-planted
AuburnFeb 10 – Mar 10Sept 1 – Oct 15
Bainbridge IslandFeb 15 – Mar 15Sept 1 – Oct 15
Battle GroundApr 1 – May 1Spring-planted
BellevueJan 15 – Feb 15Oct 1 – Dec 31Now
BellinghamFeb 15 – Mar 15Not listed
Bonney LakeMar 1 – Apr 1Not listed
BothellJan 15 – Feb 15Oct 1 – Dec 31Now
BremertonFeb 15 – Mar 15Sept 1 – Oct 15
BurienJan 1 – Feb 1Oct 1 – Dec 31Now
BurlingtonFeb 10 – Mar 10Not listed
CamasFeb 10 – Mar 10Oct 1 – Dec 31Now
CentraliaMar 15 – Apr 10Not listed
CheneyMay 1 – 30May 1 – June 10
CovingtonMar 15 – Apr 10Spring-planted
Des MoinesJan 1 – Feb 1Oct 1 – Dec 31Now
East WenatcheeFeb 15 – Mar 15Not listed
EdgewoodJan 15 – Feb 15Sept 1 – Oct 15
EdmondsJan 15 – Feb 15Oct 1 – Dec 31Now
EllensburgApr 10 – May 1Spring-planted
EnumclawMar 1 – Apr 1Not listed
EverettFeb 10 – Mar 10Not listed
Federal WayJan 15 – Feb 15Sept 1 – Oct 15
FerndaleFeb 15 – Mar 15Not listed
FifeJan 15 – Feb 15Sept 1 – Oct 15
Gig HarborJan 15 – Feb 15Oct 1 – Dec 31Now
GrandviewApr 1 – May 1Spring-planted
IssaquahJan 15 – Feb 15Oct 1 – Dec 31Now
KelsoMar 1 – Apr 1Sept 1 – Oct 15
KenmoreJan 15 – Feb 15Oct 1 – Dec 31Now
KennewickFeb 15 – Mar 15Not listed
KentFeb 10 – Mar 10Sept 1 – Oct 15
KirklandJan 15 – Feb 15Oct 1 – Dec 31Now
LaceyApr 1 – May 1Spring-planted
Lake Forest ParkJan 15 – Feb 15Oct 1 – Dec 31Now
Lake StevensFeb 10 – Mar 10Not listed
LakewoodJan 15 – Feb 15Oct 1 – Dec 31Now
Liberty LakeApr 1 – May 1Spring-planted
LongviewMar 1 – Apr 1Sept 1 – Oct 15
LyndenMar 15 – Apr 10Spring-planted
LynnwoodJan 15 – Feb 15Oct 1 – Dec 31Now
Maple ValleyMar 15 – Apr 10Spring-planted
MarysvilleFeb 10 – Mar 10Not listed
Mercer IslandJan 15 – Feb 15Oct 1 – Dec 31Now
Mill CreekJan 15 – Feb 15Oct 1 – Dec 31Now
MonroeMar 15 – Apr 10Spring-planted
Moses LakeApr 1 – May 1Spring-planted
Mount VernonFeb 10 – Mar 10Not listed
Mountlake TerraceJan 15 – Feb 15Oct 1 – Dec 31Now
MukilteoJan 15 – Feb 15Oct 1 – Dec 31Now
NewcastleJan 15 – Feb 15Oct 1 – Dec 31Now
Oak HarborJan 15 – Feb 15Sept 1 – Oct 15
OlympiaApr 1 – May 1Spring-planted
PascoApr 1 – May 1Spring-planted
Port AngelesJan 15 – Feb 15Oct 1 – Dec 31Now
Port OrchardFeb 15 – Mar 15Sept 1 – Oct 15
Port TownsendJan 1 – Feb 1Oct 1 – Dec 31Now
PoulsboFeb 15 – Mar 15Sept 1 – Oct 15
PullmanApr 10 – May 1Spring-planted
PuyallupMar 1 – Apr 1Not listed
RedmondJan 15 – Feb 15Oct 1 – Dec 31Now
RentonJan 15 – Feb 15Oct 1 – Dec 31Now
RichlandMar 1 – Apr 1Spring-planted
RidgefieldApr 1 – May 1Spring-planted
SammamishFeb 15 – Mar 15Sept 1 – Oct 15
SeaTacJan 1 – Feb 1Oct 1 – Dec 31Now
SeattleJan 15 – Feb 15Oct 1 – Dec 31Now
Sedro-WoolleyFeb 15 – Mar 15Sept 1 – Oct 15
SheltonApr 1 – May 1Spring-planted
ShorelineJan 15 – Feb 15Oct 1 – Dec 31Now
SnohomishFeb 10 – Mar 10Not listed
SnoqualmieFeb 15 – Mar 15Sept 1 – Oct 15
SpokaneApr 1 – May 1Spring-planted
Spokane ValleyApr 1 – May 1Spring-planted
SumnerMar 1 – Apr 1Not listed
SunnysideApr 1 – May 1Spring-planted
TacomaJan 15 – Feb 15Sept 1 – Oct 15
TukwilaJan 1 – Feb 1Oct 1 – Dec 31Now
TumwaterApr 1 – May 1Spring-planted
University PlaceJan 15 – Feb 15Oct 1 – Dec 31Now
VancouverFeb 15 – Mar 15Sept 1 – Oct 15
Walla WallaFeb 15 – Mar 15Not listed
WashougalFeb 15 – Mar 15Oct 1 – Dec 31Now
WenatcheeFeb 15 – Mar 15Not listed
West RichlandMar 1 – Apr 1Spring-planted
WoodinvilleJan 15 – Feb 15Oct 1 – Dec 31Now
YakimaMar 1 – Apr 1Spring-planted
YelmApr 1 – May 1Spring-planted

Planting dates: USDA Home and Garden Bulletin No. 9 (1967), tables 4 and 5. Frost dates: NOAA U.S. Climate Normals 1991–2020. The full USDA table for onion plants.