When to Plant Grass Seed in Spring: Soil Temperature Dates Where You Live

Plant cool-season grass seed in spring as early as you can work the soil, so it is already down when the top 2 inches of soil reach about 50°F: in a typical year that is around March 20–26 in St. Louis, Washington and Philadelphia, early to mid-April from New York and Columbus to Chicago and Boston, and late April in Minneapolis and Fargo. Warm-season seed such as Bermuda grass waits for 65°F soil 4 inches down, usually mid-March to late April across the South.

Those dates come from NOAA’s own soil thermometers. We read 12 springs of measured soil temperature at 41 NOAA climate stations, found the air temperature that tracks it, and applied that rule to 32 cool-season and 16 warm-season cities.

The soil temperatures that start spring seed

Cool-season seed (Kentucky bluegrass, tall fescue, perennial ryegrass) begins to sprout as soil warms to 50–55°F, according to Purdue’s turf program.⁵ Purdue’s spring seeding guide counts germination time from the day soil reaches 55°F.³ Because nothing happens below that, Purdue’s advice is to get seed down before the soil warms:⁴

Seed as soon as possible (now is not too early)

Warm-season grasses need much warmer ground. UGA Extension says to seed them when soil at the 4-inch depth is consistently 65°F and rising, typically mid- to late spring.⁷

When to plant grass seed in spring, city by city

The table gives typical-year dates for the weather station nearest each ZIP code.² “Tall fescue up by” adds Purdue’s 21-day upper germination time to the 55°F date. “Highs reach 80°F” marks the heat above which Nebraska Extension says cool-season seed is less likely to grow well.⁸

Seed in the weeks before the 50°F date if the ground is workable. Purdue notes that spring rain often makes it hard to seed after March in Indiana, and the University of Nebraska says the same for much of the Great Plains.^3,15 For any other ZIP code, our frost date lookup shows your nearest station.

How we turned air temperature into soil temperature

NOAA’s Climate Reference Network measures soil temperature at five depths at stations placed in open sites.¹ For each station we found the median date, over 2014–2025, when the top 2 inches first averaged 50°F for five days. On that date the normal daily average air temperature was about 48°F at the median station. Soil reached 55°F at about 53°F, and 65°F at 4 inches at about 63°F. So, roughly, the top few inches of soil run about 2°F warmer than the normal daily average in spring.

Re-estimated with each station left out in turn, the rule landed within a week at 22 of 35 stations; the median miss was 4½ days. It runs late in the upper South, where soil warmed up to three weeks sooner than it predicts, and early in far northern Minnesota.

Does it match extension advice?

Each extension window sits just ahead of, or on top of, the date the soil actually warmed nearby, which is what “seed early” means in practice.

Check the soil, not the calendar

Any city date is a typical year. At the median station, the earliest and latest springs were 31 days apart; at Bedford, Indiana, the date ran from March 8 to April 15.¹ In a cold spring, seed sown on the usual date can sit for weeks. A soil thermometer, or that week’s forecast, tells you more than the date.

Is March or April too early to plant grass seed?

For cool-season grass, usually not, as long as the ground is thawed and dry enough to rake. Seed just waits for warm soil. Purdue’s April 2 advice for Indiana was that seed sown then would germinate in mid to late April,⁶ and K-State expects at least two to three weeks, or more, for it to emerge in spring.¹⁰ Where soil reaches 50°F in late March, as in St. Louis or Washington, March seeding is on time. In Minneapolis or Fargo, seed sown in March sits for about a month, so you lose nothing by waiting until the ground can be worked in April.

For warm-season grass, March is too early almost everywhere outside the Gulf Coast and the desert Southwest: in Table 4 only Houston, Jacksonville and Phoenix reach 65°F soil before mid-March.

Why spring seeding is harder: the weeks before summer heat

Across 26,208 ZIP codes with a cold spring and summer highs above 80°F, normal highs hit 80°F a median 53 days after the soil reaches 55°F.² Subtract germination time and tall fescue seedlings get about 4.6 weeks of mild weather, Kentucky bluegrass about 3.6. In 89% of those ZIP codes, tall fescue gets less than six weeks.

Seeding in spring is very difficult and often unsuccessful.

That is why Purdue puts the best seeding window in mid-August to mid-September.³ In spring, Purdue finds tall fescue and perennial ryegrass more successful than Kentucky bluegrass, which germinates slowly; it suggests a 90:10 tall fescue–bluegrass mix or an 80:20 bluegrass–ryegrass mix.⁶ Shallow spring roots also need summer water:

not to even attempt spring seeding unless you are committed to watering during the summer

Warm-season grass: wait for 65°F soil

Bermuda grass, zoysia and centipede go in later, once soil 4 inches down holds 65°F. These dates use the 63°F daily-average rule:

Finish in time to let seedlings mature before frost. The University of Tennessee says to plant Bermuda grass, zoysia and centipede seed between May 1 and June 30;¹³ Oklahoma State gives May 1 to June 15 for seeded Bermuda grass;¹⁴ UGA says no later than early to mid-August in Georgia.⁷ Not sure which type you have? See cool-season vs. warm-season grass.

Spring seeding and crabgrass preventers

Spring seed and crabgrass sprout in the same weeks. Illinois Extension says crabgrass germinates once soil stays above 55–60°F for 7–10 days, and that crabgrass preventers also damage germinating grass seed, with the exception of siduron.¹²

• At seeding: siduron can go down with the seed, but Purdue says it controls crabgrass for only three or four weeks.³
• After seeding: Purdue advises waiting until new grass has been mowed four to eight times before other preventers.³ K-State notes that dithiopyr can go down in early to mid-May; some labels allow it two weeks after germination or once grass is 2 inches tall.¹⁰

Our pre-emergent timing guide has the crabgrass window for each city.

How to seed a lawn in spring

• Loosen the surface. Seed needs to touch soil. Purdue suggests raking, power raking or core aeration first; our aeration guide has the timing.³
• Feed at seeding. Purdue suggests a high-phosphorus starter fertilizer.³
• Keep it moist. Purdue advises watering three to four times a day once soil reaches 55°F, then less often but deeper as roots grow, through the summer.³ See how much to water a lawn.
• Mow early. Purdue starts at about 2 inches, then raises the mower to normal height.³

Spring or fall?

If the lawn can wait, late summer is still the better bet: find your last safe day to overseed. In the North, dormant seeding in winter puts seed down before spring even starts.

Related guideWhen to Overseed Your Lawn: The Last Safe Day Where You Live

How we worked out these dates, and their limits

Soil dates come from NOAA USCRN daily soil temperature at 5 cm and 10 cm, 2014–2025, using a five-day average.¹ City dates apply our air rule to NOAA NCEI 1991–2020 monthly normals interpolated to days.² Your soil can differ: sun, shade, slope and soil type all change how fast it warms. See our methodology page.