When to plant onion in Spokane
Onion is cold-hardy, so every date keys off Spokane's frost dates of Apr 30.
Step 1 · Sow
Start seeds indoors
Feb 19 – Mar 12
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
May 1 – May 22
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 30 – Aug 19
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Spokane's 162-day season leaves this much room.
Onion on Spokane's growing year
Frost-bounded season with crops mapped onto the 12-month axis.
Frost risk Growing Harvest
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
FROST
FROST
APR 30
OCT 9
Common questions
When will onion be ready to harvest in Spokane?
Expect to harvest from around late July (Jul 30–Aug 19) in Spokane, based on its local frost dates. Confidence 77%.
When should I start onion seeds indoors in Spokane?
Start seeds indoors around mid February (Feb 19–Mar 12) in Spokane, based on its local frost dates. Confidence 82%.
When can I transplant onion outdoors in Spokane?
Transplant outdoors around early May (May 1–May 22) in Spokane, based on its local frost dates. Confidence 83%.
How long is the growing season in Spokane?
Spokane has roughly 162 frost-free days, which is enough time to grow onion to maturity outdoors.
The rule of thumb
Sow onion as soon as the soil is workable — it tolerates cool weather and light frost. Every date on this page is derived from that rule and Spokane's frost dates.
Confidence 86/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.