How to Mow Your Lawn in Hot Weather and Keep It Green

Adjusting the deck height throughout the season is key to a healthy lawn

By Tobie Stanger

Feeling the summer heat? When temperatures soar, it’s time to rethink how you mow your lawn.

Although a low-cut, manicured lawn might seem ideal, turf grass actually does better in the summer heat when you let it grow a bit. Longer shoots mean deeper roots, which the lawn needs to suck up whatever moisture is in the soil. A higher lawn also shades the soil, minimizing evaporation.

To allow your grass room for growth, you’ll need to raise the height of your lawn mower’s deck—that is, the machine’s main body, which houses the blade. Lawn mowers today, including the top-scoring models in our lawn mower ratings, have height adjustment levers that make it easy to raise and lower the deck. You’ll need to use a ruler to determine the precise setting, at least until you get familiar with it.

During the spring growing season, CR recommends letting grass grow to about 4½ inches before mowing it back to 3 or 3½ inches. When the heat starts to ease off later in the season, you can drop down to 2½ inches for a more manicured look. Here are step-by-step instructions for how to adjust and clean your lawn mower’s deck to keep both your mower and your lawn in peak condition.

Step 1: Measure Current Cutting Height

Roll the mower onto a level surface, like a driveway or garage floor. If it’s a battery-powered mower, make it doesn’t start up while you’re working by removing the battery and safety key. To take the same precaution with a gas mower, detach the spark plug wire from the spark plug; it’s typically on the front of the mower. “The wire is insulated by a rubber casing and takes some wiggling to get off,” says John Galeotafiore, head of Consumer Reports’ home improvement testing. “But it’s not that hard to do, and the wire and its casing reattach easily to the spark plug.”

Lift up the side- or rear-discharge flap covering the opening that expels cut grass. You’ll see the blade inside. Determine the current blade height by measuring the distance between its bottom edge and the ground.

It’s worth noting that most manufacturers ship mowers from the factory with the deck in the lowest position—often as low as 1½ inches, which can scalp a lawn even during ideal weather conditions.

Step 2: Adjust the Deck Height

Lawn mowers come with notched adjustment levers that raise and lower the wheels, thus changing the distance between the deck and the ground. For walk-behind mowers, there may be one lever for each wheel, one lever for the rear wheels and another for the front wheels, or a single lever for all four wheels. With riding mowers, one lever moves the deck up and down, independent of the wheels.

We find that all configurations are easy to operate once you get the hang of it. But the notches don’t always provide a corresponding cutting height, so it doesn’t hurt to take a measurement with your ruler after making the adjustment to ensure your lawn mower blade is at the correct cutting height.

Step 3: Clean the Deck

Grass clippings tend to stick to the underside of the deck, especially if the lawn is damp. If the clumps get bad enough, they can start to restrict airflow inside the deck, which will compromise cutting performance. Dried clippings and clumps are a pain to remove, so it’s best practice to clean the deck after each mowing.

Some mowers have a washout port where you can connect your hose, though a plain old rag will also do the trick. Just be sure to wear heavy gloves to protect your hands from getting cut by the blade. Each time you do this, play it safe by again removing the spark plug wire of a gas mower or the safety key of a battery-powered machine.

To. help prevent future buildup when cutting grass, coat the cleaned, dried deck with silicone spray, available at home centers or hardware stores. And keep an eye on the blade’s sharpness. Ideally, have it sharpened—at a hardware store or lawn mower dealer—at the start of the season and at least one more time during the season, especially if you have sandy or rocky soil.

“Sandy soil acts like an abrasive and will dull the blade more quickly,” Galeotafiore says. “With rocky soil, there’s the possibility you can hit small stones and cause the blade to dull or chip.”

If the blade is very dull, you can replace it yourself without a lot of effort. (Watch "How to Remove and Replace a Lawn Mower Blade" for our guide to this essential maintenance.)

CR members with digital access can see ratings and reviews below of our top picks for walk-behind mowers that will keep grass trimmed to the perfect height. We’ve highlighted below both push and self-propelled gas- and battery-powered mowers (as well as one wide-deck model) that perform well across the board and rate highly in our evenness test, ensuring a uniform, carpetlike cut. Also, check out our lawn mower buying guide for tips on how to find the right mower for your lawn.

Best Battery Mowers for an Even Cut

Best Gas Mowers for an Even Cut

Finding the Perfect Lawn Mower

Is your lawn mower failing to make the cut? On the "Consumer 101" TV show, Consumer Reports expert John Galeotafiore explains to host Jack Rico how to find the best mower for your needs.

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