When to plant onion in Aurora
Onion is cold-hardy, so every date keys off Aurora's frost dates of May 5.
Step 1 · Sow
Start seeds indoors
Feb 24 – Mar 17
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
May 2 – May 23
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jul 31 – Aug 20
Picking runs until conditions turn against the crop.
Window
Days to maturity
90 – 110 d
Aurora's 152-day season leaves this much room.
Onion on Aurora'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
MAY 5
OCT 8
Common questions
When will onion be ready to harvest in Aurora?
Expect to harvest from around late July (Jul 31–Aug 20) in Aurora, based on its local frost dates. Confidence 80%.
When should I start onion seeds indoors in Aurora?
Start seeds indoors around late February (Feb 24–Mar 17) in Aurora, based on its local frost dates. Confidence 85%.
When can I transplant onion outdoors in Aurora?
Transplant outdoors around early May (May 2–May 23) in Aurora, based on its local frost dates. Confidence 86%.
How long is the growing season in Aurora?
Aurora has roughly 152 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 Aurora's frost dates.
Confidence 89/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.