When to Plant Grass Seed in Pennsylvania

Cool-season lawns dominate Pennsylvania, and for cool-season seed fall is the better window, with spring the second choice. The dates below are typical crossings from in-state monitoring stations; your city page tracks the live reading.

Best Time to Plant Grass Seed in Pennsylvania

Cool-season · fall window

August 31

August 20 (coolest parts) to September 9 (warmest)

For cool-season lawns (fescue, bluegrass, ryegrass), fall is the best time to plant grass seed in Pennsylvania, with spring the second choice: fall seedlings face less weed competition and mature before summer heat. The window opens as 2-inch soil falls back through 70°F, and germination slows sharply once soil drops below 50°F, typically around November 2. Fall seeding and fall pre-emergent are an either/or on the same turf; see pre-emergent timing in Pennsylvania.

Cool-season · spring window

April 1

March 31 (warmest parts) to April 11 (coolest)

Spring is the second choice: the window opens when soil first holds 50°F and narrows as soil passes 65°F, typically by May 26.

Fall seeding also needs a stop date: new seedlings want about six weeks of growth before frost arrives. Your city page estimates the last safe seeding date from its nearest station: see when to plant in Philadelphia, when to plant in Pittsburgh or when to plant in Erie. Today's statewide reading is on the Pennsylvania soil temperature page.

Typical dates are computed from historical 2-inch soil temperature averages at 3 monitoring stations in Pennsylvania; your own window depends on your nearest station's readings.

Best Time to Plant Grass Seed in Pennsylvania: Month by Month

Typical 2-inch soil temperature by month across Pennsylvania, the median of 3 in-state stations with multi-year records, with the seeding verdict for each grass family. Confirm against the current reading on your city page before you put seed down.

Month	Typical 2" soil temp	Cool-season seeding	Warm-season seeding
January	34°F	Dormant	Too cold
February	34°F	Dormant	Too cold
March	42°F	Too cold	Too cold
April	52°F	Good; fall is better	Too cold
May	62°F	Good; fall is better	Approaching
June	70°F	Risky; heat ahead	Prime window
July	76°F	Too hot	Prime window
August	73°F	Soon; still cooling	Too late this year
September	67°F	Soon; still cooling	Too late this year
October	55°F	Prime window	Too cold
November	45°F	Too cold	Too cold
December	37°F	Dormant	Too cold