When is it too hot to mow your lawn? Look for these 4 warning signs

Many of us love the sense of accomplishment we get from garden tasks such as planting, deadheading, pruning, and harvesting. But mowing usually is another matter! Granted, sometimes it’s too hot for you to mow, so give yourself permission to postpone the chore. Your grass isn’t going anywhere! But if you’re wondering whether mowing when it’s too hot is bad for your grass, we asked the experts.

First, you need to know what kind of grass you have. “In general, warm season grasses, such as Zoysiagrass and Bermudagrass, grow in climates where summers are hot and dry or hot and humid and winters are mild,” says Clint Waltz, PhD, turfgrass researcher and extension specialist at the University of Georgia. “Cool season grasses, such as Kentucky bluegrass or tall fescue, typically grow in northern climates where summers are mild and winters are cold.”

You also may have a mixture of warm and cool season grasses in the transition zone, which has no specific borders, but is generally considered the mid-section of the country. Both types of grasses can grow there, says Waltz. If you aren’t sure what you have in your yard, your local university coop extension service (find yours here) can help you identify them.

Read on to learn whether mowing during a heat wave can damage your turf:

How Cool Season Grasses Take the Heat

Cool season grasses are happiest in the spring and fall, growing vigorously when temperatures aren’t super-hot. “During peak periods of growth in the spring, you may need to mow your lawn more than once a week,” says Peter Landschoot, PhD, professor emeritus of turfgrass science at Penn State University College of Agricultural Sciences. “But that’s not the case in the heat of midsummer. Cool season grasses aren’t growing much except a patch here and there.”

That means you shouldn’t mow on a schedule, say, every Saturday morning. Instead, watch your lawn. If it’s been hot and dry, especially with temperatures in the high 80s and 90s, you won’t need to mow until active growth resumes following rainfall. “The bottom line is that when your turf is under heat and drought stress, mow as infrequently as the grass allows,” says Landschoot.

If you mow during a heat wave, you can damage the crown where growth originates. “Turf is much more susceptible to physical pressure if you mow when it’s drought-stressed,” says Landschoot. The weight of the mower—or even walking on drought-stressed lawns—may leave lines and visible damage from which it takes weeks (or more!) to recover.

If you live in the mid-section of the country and a have mix of warm and cool grasses, you’ll want to follow cool season mowing rules, that is, reduce mowing frequency so that you’re not causing additional stress to your lawn.

Of course, if you’re irrigating and your grass is lush and green, you can go ahead and mow. But save this chore for the evening, when the day’s heat has eased and the grass is dry. Dry grass is less likely to cake up under the mowing deck, and you’ll also get a more even cut, says Landschoot. Plus, it’s easier on you!

How Warm Season Grasses Take the Heat

Warm season grasses are adapted for hot climates and don’t mind the heat, so it’s really never too hot to mow healthy warm season grasses—except for your own comfort. “If your grass is well-watered because you’ve been irrigating, or you have had some rain, it’s fine to mow any time,” says Waltz.

Warm season grasses are growing actively this time of year, so there’s no detrimental effect if you choose to mow on a hot day. It’s fine to cut a healthy warm season lawn, even in the middle of the day, should you choose to do so, says Waltz.

When It’s Too Hot to Mow—No Matter Your Grass Type

Of course, there are times when it’s not a good idea to mow any type of grass, and you should postpone a cut. Pay attention to the weather. For example, if you’re expecting a few days of extreme heat and/or no rain ahead, it’s fine to hold off on mowing until you get through the worst of it, says Landschoot.

4 Signs to Watch For:

You also should postpone mowing if you notice these signs of stress in your turf, say Waltz and Landschoot:

• The turf color is “off” or has a bluish-gray caste to it from heat and drought stress.
• The grass is brown or yellowish-brown from heat and drought stress.
• The grass hasn’t grown much since your last cut.
• The grass doesn’t look healthy. Use common sense; if it doesn’t look good, it’s probably stressed and mowing only adds insult to injury.

5 Tips to Protect Your Lawn from Heat

Turf is incredibly resilient, more so than you might think. But following these tips from Waltz and Landschoot will help your lawn survive the worst of summer’s heat and drought stress:

1. Don’t scalp your lawn. Mowing too low can damage the crown and cause thinning grass so weeds encroach. Keep the mower deck at the upper end of the ideal mowing range for your grass species (check with your local university cooperative extension for the best heights for your species and region).
2. Irrigate properly. Water deeply in the morning so it’s less likely to evaporate. Also, you don’t need to water every day. Most lawns need roughly 1 inch of water per week, though sandy soils, which drain rapidly, need about 1½ inches per week.
3. Sharpen your mower blades. Dull blades tear, rather than cut, grass. A poor quality cut looks shaggy and makes your grass vulnerable to stress from disease and insects. You may need a mid-season second sharpening. Most mower blades can be removed and taken to a small engine repair shop.
4. Let clippings stay put. If you have a mulching mower, it’s not necessary to pick up clippings; allow them to decompose, which adds nutrients back to the soil.
5. Be realistic. Your lawn isn’t a putting green, so don’t expect perfection. Go ahead and enjoy the summer, take a day off when it’s stifling—and have a lemonade instead of mowing!