Mowing the Lawn in Hot Weather: How Hot is Too Hot?

It’s getting pretty hot in here, huh?

As more parts of the world start to experience extreme temperatures, more people are starting to wonder: when is it too hot to mow the lawn?

Luckily for us, hot weather actually means less yard work, at least as far as mowing the lawn is concerned.

I’m going to explain when you shouldn’t cut your grass, when it’s ok to, and what height to cut it when you do.

The longer answer is that there are a few things to consider. If you want the more detailed version, with extra tips on how to keep your lawn healthy through the heat, keep reading.

When is it Too Hot to Mow the Lawn?

The things that you should consider when deciding when to cut your lawn in hot weather are:

The main reason you shouldn’t cut your grass in really hot weather I s because your lawn is likely already stressed. If you mow it, you are increasing its stress level, and an overly stressed lawn will start to die off.

The best way to look after your lawn and promote its health, is to minimize the stress that it experiences.

When and how short you mow can be the deciding factor in how stressed your lawn gets at various times of the year.

Warm Season Versus Cool Season Grasses

Lawn grass species are divided into either cool-season and warm-season grasses.

How you look after your lawn in hot weather depends a lot on whether it is a cool or warm season variety.

Since most lawn species are cool-season grasses, they are unlikely to be growing in the heat of summer. This means you shouldn’t need to mow your lawn much, or at all, in hot weather.

The most sensible thing you can do for your lawn is to leave it alone when the weather is consistently above 80˚F.

Warm season grasses, on the other hand, will likely be growing, and will handle additional stress in hot weather that cool season grasses won’t.

If your warm season grass needs a trim, you’re not restricted by temperature to the same degree (pun intended!), but it’s still a good idea to wait until the evening, or a cooler day.

Is Your Lawn Dormant?

If your lawn is composed of cool-season grasses, it will likely go dormant in the summer.

This means that it will be under stress in the heat and will allow its leaves to go yellow in order to survive the summer. It may look dead, but it’s not. Instead, it has transferred its energy and moisture to its roots.

If your grass is dormant, you shouldn’t mow it. Instead, resist the temptation and wait until the weather has cooled. It’s safe to mow again once you have noticed some visible signs of growth and green returning.

While trying to revive dormant yellow grass in the heat of summer is also tempting, you may do a disservice to your lawn and the environment.

Unless you have ample access to water and can maintain a twice-weekly irrigation schedule to support your lawn until temperatures cool, bringing it out of dormancy could cause it more stress.

This is because if you bring a lawn out of dormancy, it will try to grow again, and growth requires water. If there isn’t enough water, your lawn will have to go through another period of stress before it enters dormancy all over again.

In saying that, you can support a dormant lawn’s survival by giving it a little water every now and then, just not enough to trick it into thinking it’s safe to come out of dormancy.

Does Your Lawn Have Access to Water?

In keeping with the above, the amount of water that your lawn is receiving is also a deciding factor in whether or not you should mow in hot weather.

If your region is experiencing hot temperatures and water shortages, then your lawn is likely dehydrated.

If your lawn is dehydrated but not yet dormant, it is definitely under stress. (In fact, this is called lawn heat stress and I have an article all about it here.) This means that mowing is a bad idea, even in the evening when temperatures are cool.

The best course of action is to wait until temperatures have cooled and there has been some rain.

Alternatively, you can mow with your mower set much higher than normal. This will help to even things out without stressing your lawn too much.

If you desperately need to cut your lawn to a shorter height, say for a special event like a wedding or big birthday, then plan ahead a little. If you give your lawn a couple of good drinks in the week before cutting, you can minimize the stress that cutting will cause.

Of course, be mindful of whether there are any water restrictions in your region before doing this!

It is increasingly frowned upon to use municipal water supplies for lawn irrigation, so think twice before watering, and have a read of this guide to lawn watering to make sure you’re doing it right.

How Short to Mow in Hot Weather

If you’ve got this far, you’ve decided that your lawn isn’t unduly stressed and will handle a haircut. But how short should you go?

Later on, when things cool down and the grass enters its active growing phase again, you can go shorter (2.5 inches).

However, these numbers are only relevant if your grass wasn’t too long to begin with.

If your grass has got significantly longer than 4-5 inches, then cutting to 2.5 or 3.5 inches isn’t going to be helpful. This is because removing more than the top third of a blade of grass is a bad idea.

The middle third of a blade of grass is where the magic of photosynthesis happens, and if you eat into this area, your grass is going to have a hard time getting the energy it needs to keep going.

Have a read of this guide to grass cutting heights if you’re interested in learning more.

And while we’re on the subject, do you need a new mower? I have guides and reviews of every mower you could think of, so look no further! I’ve got you covered, whether it’s battery-powered mowers, ride-on mowers, commercial zero-turn mowers, or mowers for small yards!

If you’re looking for a lawnmower on a budget, I have a great list of cheap lawn mowers to help you.

Or, if you’re unsure what kind of lawn mower you need, I have a guide to the different lawn mowers that is an essential read.

A Few More Tips

Don’t Fertilize During the Hot Season

Applying fertilizer or selective herbicides on your lawn while it is dormant in the summer will likely do more harm than good. It’s vital to only fertilize plants during their active growing season, which for cool-season grasses is fall or spring.

The exception would be if your lawn is composed of warm-season grass and your region is experiencing enough rain for healthy growth. Then, by all means, give your lawn a feed in the summer.

Leave the Clippings as Mulch

If you mow your lawn and the volume of cut grass isn’t too great, leave the grass clippings on the lawn as mulch (assuming they have sprinkled nicely and aren’t clumped).

They will return their nutrients to the ground and help to retain moisture in the soil. Check out this article for more ideas on what to do with grass clippings.

Reduce Other Forms of Lawn Stress

Remember, hot weather usually means stress for cool season lawn grasses. So, it pays to do what you can to minimize other forms of stress that your lawn might be subjected to as well.

These include foot traffic, lawn furniture and kids’ toys. Keeping these things to a minimum, and changing the position of what lawn furniture you do have from time to time, is helpful for your lawn.

Use a Lawn Care Calendar

There is a lot to think about when it comes to lawn care, and using a calendar like the one I’ve put together here can simplify the year and make it easy to keep track of what you might want to be doing and when.

Take Care of Yourself

Heat exhaustion is no joke, and strenuous physical activities like mowing in hot weather puts you at risk of heat-related illnesses.

How does this happen?

While the body usually cools itself through sweating, this might not be enough in extreme heat. Your body temperature will rise faster than it can cool itself, leading to heat exhaustion or heat stroke.

Symptoms can include fatigue, nausea, light-headedness, dizziness, and heavy sweating. If you must mow in the summer heat, ensure you wear sunscreen, take breaks, and hydrate often.

You might also consider a riding mower if you have a large area to mow. This makes mowing easier and more enjoyable in hot weather. It eliminates a lot of the physical labor from the task!

Keep Your Tools Sharp

Lastly, make sure your lawnmower is up to the job and well maintained. If you need to brush up on your lawn mower maintenance skills, read this article.

FAQs

Is 90 degrees too hot to mow?

Yes, 90 degrees is definitely too hot to mow. If your lawn desperately needs cutting, then wait until the evening, or better still, until the weather has cooled down.

Should you cut grass before a heat wave?

No. Cutting your grass before a heat wave is a bad idea. Mowing your lawn puts it under stress. Being exposed to hot temperatures also puts it under stress. The best thing you can do for your lawn before a heat wave is to leave it long.

Is it better to leave grass longer in hot weather?

Yes, it is much better to leave grass longer in hot weather. This is because long grass equals longer roots, which equals more access to moisture deeper in the soil. Longer grass also helps to shade the soil and reduce moisture lost through evaporation.

What time of day to mow in hot weather?

The best time of day to cut grass in hot weather is at night after temperatures have dropped.

Mowing in the evening allows the grass to have the cool nighttime to recover and hopefully benefit from a bit of morning dew before the day’s heat returns to stress it all over again. It gives the grass enough shade and healing time before the next sunrise.

In saying that, there are some schools of thought that discourage evening mowing because of the increased risk of fungal infections attacking your lawn at night. However, if we’re talking heat wave temperatures, the chances of fungal infections occurring are pretty low.

Some lawn species are more prone to fungal infections than others, so knowing what kind of grass you have is also helpful for this.

How often should you cut grass in summer?

The answer to this question depends on how quickly your lawn is growing. If your lawn is dormant, you’re not going to be cutting it at all. Rather than sticking to a schedule, it’s better to remain observant and mow your lawn when it gets to a certain length.

Since you don’t want to remove more than a third of your lawn’s length in one go, you want to mow it when it’s approximately an inch or two longer than where you want it.

Should I water lawn every day in hot weather?

No, you definitely shouldn’t water your lawn every day in hot weather, or ever for that matter. It is best to water twice per week and deeply, as this encourages deep, strong root formation. Watering daily results in shallow roots and a less resilient lawn.

Should I water after mowing?

It is ok to water after mowing but not necessary, and not sensible in the heat of summer either. Since its recommended to water early in the morning, it’s more logical to water the morning after mowing.

Does cutting grass in heat kill it?

While a one off trim in hot weather is unlikely to completely kill your lawn, it will cause it stress which will make it harder to survive the remaining summer. It might also take longer to recover when fall arrives.

Summary

You might have been surprised to learn that less is more for lawn care in the summer heat. (That is unless you have a warm-season grass species on your lawn.)

Save your mowing until the evening, mow a little longer, and limit the amount of use that one particular patch of grass gets to spread the load.

If you’re still wondering, when is it too hot to mow the lawn? Then just think about whether you want to be cutting grass in hot weather. If it’s too hot for you, it’s too hot for your lawn!

Thank you for reading and as always, feel free to share your thoughts in the comments below. I love hearing from you!