When to plant summer squash / zucchini in Philadelphia

Summer squash / Zucchini is frost-tender, so every date keys off Philadelphia's last spring frost of Mar 28.
Step 1 · Sow
Start seeds indoors
Mar 27 – Apr 17
Before your last frost, on a warm windowsill or heat mat.
Step 2 · Plant
Transplant outdoors
Apr 30 – May 21
Once frost risk has passed and nights stay mild.
Step 3 · Harvest
Harvest window
Jun 14 – Jun 29
Picking runs until conditions turn against the crop.
Window
Days to maturity
45 – 60 d
Philadelphia's 234-day season leaves this much room.
Summer squash / Zucchini on Philadelphia'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
MAR 28
NOV 22

Common questions

When can I sow summer squash / zucchini outdoors in Philadelphia?

Direct-sow around late April (Apr 30–May 21) in Philadelphia, based on its local frost dates. Confidence 84%.

When will summer squash / zucchini be ready to harvest in Philadelphia?

Expect to harvest from around mid June (Jun 14–Jun 29) in Philadelphia, based on its local frost dates. Confidence 78%.

When should I start summer squash / zucchini seeds indoors in Philadelphia?

Start seeds indoors around late March (Mar 27–Apr 17) in Philadelphia, based on its local frost dates. Confidence 83%.

When can I transplant summer squash / zucchini outdoors in Philadelphia?

Transplant outdoors around late April (Apr 30–May 21) in Philadelphia, based on its local frost dates. Confidence 84%.

How long is the growing season in Philadelphia?

Philadelphia has roughly 234 frost-free days, which is enough time to grow summer squash / zucchini to maturity outdoors.

The rule of thumb

Sow summer squash / zucchini 6–8 weeks before your last spring frost; plant out 2–3 weeks after it. Every date on this page is derived from that rule and Philadelphia's frost dates.

Confidence 87/100 · Curated · based on NOAA GHCN-Daily 1991–2020 normal · frost dates are probabilities, not guarantees.