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When to Aerate Your Lawn by Zone

Core aeration pulls small plugs of soil out of the lawn so air, water and fertilizer reach the roots. It does some damage at first, so it is done when the grass can recover fast: early fall or spring for a cool-season lawn, late spring or early summer for a warm-season one, after the last frost. The table gives your zone’s freeze dates.

Published October 27, 2026 · Cite this page

Freeze dates for aerating, by zone

Clemson Cooperative Extension aerates warm-season lawns once the threat of frost has passed. Here are each zone’s median last spring freeze and the cold-year date NOAA says is passed in 9 years out of 10, from the median station, with the first fall freeze that closes a cool-season lawn’s fall window.

Zone Last spring freeze, median Last spring freeze, cold year First fall freeze, median Stations · ZIP codes
Zone 3 May 19 June 1 September 22 98 · 253
Zone 4 May 13 May 27 September 28 698 · 2,098
Zone 5 May 6 May 20 October 5 1,307 · 5,306
Zone 6 April 28 May 13 October 17 1,728 · 10,458
Zone 7 April 14 April 30 October 26 1,428 · 8,732
Zone 8 March 26 April 13 November 9 1,253 · 6,809
Zone 9 February 25 March 21 December 1 736 · 4,284
Zone 10 January 18 February 18 January 1 234 · 1,986

⚠️ The freeze date is the earliest a warm-season lawn should be aerated, not the day to do it: Clemson also waits for the lawn to green up, and NC State aerates in late spring or early summer. Clemson says green-up comes in April on the South Carolina coast and as late as mid-May inland. For your own station, enter your ZIP code below.

When, by kind of grass

SourceCool-season lawnsWarm-season lawns
Iowa StateSeptember and April—
NC StateFall or early springLate spring or early summer
Penn StateIn cool weather: early to mid-spring, or late summer to early fall—
ClemsonTall fescue, in fall, where traffic or clay compacts the soilOnce the threat of frost has passed; centipede and St. Augustine also once fully greened up
UGA Extension, Dougherty County—Bermudagrass, only when needed, during active growth

The reason is the same on both sides: Iowa State says core aeration does some damage at first, so it is done when the grass recovers quickly. Clemson adds, for warm-season lawns going into winter, that core aeration belongs in spring after green-up.

How to core-aerate

  1. Feed a week before. Iowa State fertilizes the lawn one week before aerating, to help it recover — on a cool-season lawn, inside that lawn’s feeding months.
  2. Wait for moist soil. Not dry, when the tines will not go deep, and not wet, when they clog (Iowa State). Penn State says the tines need moisture to pull plugs.
  3. Use hollow tines. Iowa State pulls cores about three-quarters of an inch across and 3 inches long, and avoids spike-type devices, which compact the soil.
  4. Make several passes. Iowa State aims for 20 to 40 holes per square foot, which usually takes more than one pass; NC State cores in several directions.
  5. Break up the cores. Let them dry, then pull a drag mat or a weighted piece of fencing across them (Iowa State), or break them up with a mower (NC State).
  6. Water and seed if needed. Iowa State waters afterward if the weather is dry, and overseeds or fertilizes after aerating. Before overseeding a Bermudagrass lawn with ryegrass, Clemson waits thirty days after aerating so the holes heal.

Iowa State also works a thin layer of fine compost, about a quarter of an inch, into the lawn with the aeration to improve the soil.

How often

Iowa State aerates lawns on heavy clay, or with heavy foot or pet traffic, twice a year, and lawns on well-drained soil with little traffic once a year. Clemson core-aerates tall fescue lawns with heavy traffic or clay soil, and says compacted soil stays colder than well-drained soil, which matters to a warm-season lawn going into winter. Aeration also helps keep thatch in check (Iowa State).

Supplies

Supplies the sources mention

Each link opens an Amazon search for a plain kind of product, not one we picked. We have not tested these, and we do not rank them.

As an Amazon Associate I earn from qualifying purchases. It costs you nothing extra and changes nothing on this page: the dates are NOAA’s and the advice is the extension services’. Affiliate disclosure

  • Core aeratorIowa State University Extension and Outreach says to use a core aerator, with hollow tines that pull plugs of soil, and to avoid spike-type devices; it notes core aerators are often available at rental agencies.
  • Drag matAfter aerating, Iowa State pulls a drag mat or a weighted piece of fencing across the lawn to break up the soil cores.

Your ZIP code

Your ZIP, your answer

Enter your ZIP code to see your USDA zone, the zone’s last spring and first fall freeze dates for aerating, read from the table on this page, and the freeze dates of the NOAA station nearest you.

Works for all 40,502 US ZIP codes. Freeze dates need a NOAA station within 100 km; where there is none, the page says so rather than estimating one. Your ZIP code stays in your browser: the page downloads the file of ZIP codes that share its first three digits and looks yours up there. It is not stored or tracked.

Your answer appears here.

Full details for any ZIP code: ZIP code zone finder.

Common mistakes

  • Spiking instead of coring. Iowa State says spikes compact the soil.
  • Aerating dry or soggy soil. Iowa State says the tines do not penetrate dry soil and clog in wet soil.
  • Aerating a warm-season lawn in fall or before green-up. Clemson aerates in spring, after the frost threat has passed.
  • Aerating a cool-season lawn in summer heat. Penn State aerates in cool weather, so the grass recovers quickly.
  • One quick pass. Iowa State aims for 20 to 40 holes per square foot.

Every lawn job by zone

Where there is no source here

We found no Texas or Florida source on aeration timing that we could read. The warm-season timing follows NC State and Clemson, written for the Carolinas, and UGA Extension for Georgia; for which grass you have, see cool-season vs warm-season grass.

Questions

When is the best time to aerate a cool-season lawn?
Early fall or spring, while the grass is growing well. Iowa State says September and April are the best times for Kentucky bluegrass and other cool-season lawns, and NC State cores cool-season grasses in fall or early spring.
When should I aerate a warm-season lawn?
In late spring or early summer, once it is growing. NC State cores warm-season grasses then, and Clemson’s calendars aerate Bermudagrass and zoysiagrass once the threat of frost has passed, and centipede and St. Augustine once the lawn has also fully greened up.
How often should I aerate my lawn?
Iowa State says lawns on heavy clay soil or with heavy foot or pet traffic should be aerated twice a year, and once a year is enough for lawns on well-drained soil with little traffic.
Is a spike aerator as good as a core aerator?
No. Iowa State says to avoid spike-type devices, which simply punch holes and compact the soil, and to use a core aerator with hollow tines that remove plugs.
Should the soil be wet or dry when I aerate?
Moist. Iowa State says the tines cannot go deep in dry soil and clog with soil when it is wet, so aerate when the soil is moist and avoid both extremes.

Sources

Dates on this page are computed when the site is built from NOAA's 1991–2020 Climate Normals (first fall freeze at 32 °F, for every station the ZIP codes in each zone cite). Zones are the USDA Plant Hardiness Zone Map, 2023. Every rule — how long before or after a freeze to plant, how deep, how much — is quoted from the extension publications below, each of which writes for its own area.

Nothing here replaces your own state's cooperative extension service, which knows your county. Where this site's numbers come from.

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