When to overseed, aerate, seed in spring or dormant-seed a lawn, with the last safe fall date for your city and the extension rules behind it.
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Most lawn grass seed germinates in 3 to 30 days, from about a week for ryegrass to a month for Kentucky bluegrass and Bermuda grass. NOAA’s measured soil temperatures show why early-fall seed comes up so much faster than spring seed.
Get cool-season seed down before the top 2 inches of soil reach 50°F, and wait for 65°F soil for Bermuda grass. Typical dates for 48 US cities from NOAA’s measured soil temperatures and climate normals.
Dormant seed a cool-season lawn once normal afternoon highs fall below about 40°F, and stop when they climb back. Winter windows for 23 Northern US cities from NOAA normals, checked against extension advice.
Core-aerate cool-season lawns in late summer to early fall and warm-season lawns in late spring to summer. Windows for 27 cities from NOAA normals, checked against extension calendars.
Finish overseeding at least 45 days before your first hard freeze. Dates for 21 cities, checked against extension advice, plus your own ZIP.
Most seeding failures come down to timing: seed sown too late in fall never gets established before a hard freeze. Our guides count back from the frost data for your ZIP code, compare the result with published extension windows, and give seeding rates per 1,000 sq ft from extension recommendations, so you can scale them to any lawn.
Get a short email when it’s time to overseed, start seeds, open the pool or service your furnace — timed to your climate.
