FAQ: What is heat stress in lawns?

Answer: Heat stress refers to heat and humidity with a thirsty lawn in the summer. A lawn with heat stress will wilt, turn brown, and possibly die without water.

As a homeowner, you are crucial in preventing heat stress on your lawn. Summertime brings hot, dry days that can lead to your lawn experiencing heat stress.

If you have a cool season lawn, it may brown up because it went dormant, while warm season turfgrass will eventually wilt if it gets no water to hydrate it after a few weeks.

In this blog post, you’ll learn more about heat stress and how it affects your lawn, including

• Why you must water your lawn at the right time of day
• How cool- and warm season grasses respond to heat stress
• How to effectively water your lawn.

Why You Must Water Your Lawn at the Right Time of Day

Did you know that if you water your lawn in the evening or after dark, you increase the chances that your lawn will develop fungal diseases?

As the summer progresses with increased humidity or arid conditions that include no rain, your lawn will experience heat stress.

However, suppose you wait to water your lawn until the evening. In that case, you’re putting your turfgrass at risk of fungal diseases because the water sits on the turf overnight, and the humidity encourages fungal spores to develop and spread.

Typical lawn diseases that crop up in summer from watering at night include:

• Brown patch
• Dollar spot
• Fairy ring
• Leaf spot
• Necrotic ring spot
• Pythium blight
• Red thread
• Rust
• Slime mold
• Summer patch.

What Are Cool- and Warm Season Grasses?

If you live in the northern half of the United States, you have cool season grasses, such as mixtures of Kentucky bluegrass, fescues, and perennial ryegrass.

Cool season grasses thrive in colder temperatures, and warm season grasses grow in hotter temperatures.

Warm season grasses are made up of different turfgrass blends depending on where you live in the southern part of the U.S.

For example, you probably have a Bahia or St. Augustine turf if you live along the Gulf Coast or the Southern Atlantic coastline.

Bermuda and zoysia turfgrasses are found in the southern and transitional interior of the U.S.

The transitional zone is between north and south, where cool- and warm season lawns co-exist. For example, in Maryland or Virginia, you may have a zoysia lawn in full sun, while tall fescue turf can be found in shady areas.

How Heat Stress Affects Cool- & Warm Season Turfgrasses

Summer stress combines two environmental issues that affect cool season lawns more than warm season lawns include:

• Drought stress
• Heat stress.

Drought stress occurs when there is a lack of rainfall or irrigation, affecting both cool- and warm season lawns. Photosynthesis stops, and you’ll notice your turf going from green grass to gray and then to the dormant tan color.

A drought-stressed lawn will die unless it gets some water to cool the plant and the soil as well as to provide moisture to the soil.

Your turfgrass has drought stress if it looks thinner, has discoloration, and shows footprinting, where your footprints won’t disappear for several hours after walking on your lawn.

Heat stress occurs in cool season lawns when daytime temperatures rise to 75°F and beyond. As temperatures reach the 80’s and 90’s, the grass will go dormant for up to four weeks.

Cool season turf will die after four weeks without significant rain or irrigation. However, once it starts to rain again or you turn on your automatic water sprinklers, the grass will green up.


Warm season grasses grow well with summer sun. However, during the warm season, grasses will start to wilt and then go dormant when there’s drought stress. To avoid your warm season lawn from dying, ensure that it gets at least 1½” of water per week, including any rainfall.

How to Effectively Water Your Lawn

While you may think sprinkling your lawn every evening with a garden hose or an above-ground sprinkler attached to the hose is enough to keep your turfgrass alive, you’d be wrong.

Lawns, whether they’re cool- or warm season grasses, need infrequent watering. Watering needs vary but are within the weekly 1” to 2” range. You need to include any rainfall in the total inches per week.

Warm season grasses are more drought-tolerant than cool season lawns, so they must be watered one to two times a week.

Cool season grasses get thirstier, especially in the middle of summer when the temperatures are hot and there’s little rainfall. They must be watered up to three times per week in July and August.

Your automatic sprinkler system should start watering your cool season lawn in late spring through early fall, after which you can cut back on watering as temperatures cool and there’s more rain.

Also, run your in-ground water sprinklers using the cycle-and-soak method. Turn on your sprinklers for 30 minutes, stop and let the water soak into the ground, and then turn your sprinklers back on for 30 minutes to get 1” of water.

However, if you live in Texas or the desert south, ensure you do 15 minutes per cycle instead of 30 minutes at a time. You’ll conserve water so it doesn’t evaporate in super hot conditions.

Finally, set your sprinkler timer for the early morning hours, anytime between 4 a.m. and 9 a.m., to avoid water evaporation.

How K-Rain Irrigation Products Prevent Heat Stress in Lawns

If you want to keep your lawn green and vibrant this summer, you need K-Rain.

Avoid heat stress with K-Rain's Sprinkler System Products, which transform your lawn and landscape into healthy plants. Whether you're a DIY enthusiast or seek professional expertise, our K-Rain products ensure a seamless journey to a healthy lawn and landscape.

Explore our sprinkler system products online, or buy your K-Rain products at The Home Depot and Lowe's.

Find a skilled irrigation contractor via our website for accessible installation services.

Need help with K-Rain products? Contact our customer service team at 800-735-7246 or through our contact form.

Sources:
LawnDoctor.com, Heat Stress Can Do a Number on Your Yard: What Can You Do?
LegacyTurfFarms.com, Heat Stress in Warm Season Lawns.
Scotts.com, What Are Cool Season Grasses?
Ibid, What Are Warm Season Grasses?
TheSpruce.com. How Long and How Often Should I Water My Lawn?
TurfSupplyCare.com, How to Protect and Restore Your Turfgrass from Summer Stress.