Should You Mow the Lawn in a Heatwave? Experts All Agree to Stop at This Temperature
The lawn mowing rule every gardener needs to know
Mowing is one of those classic summer jobs. However, taking the lawn mower out in a heatwave can actually damage your grass. So when is it too hot to mow? When the temperatures hit 90°F, lawn care experts warn homeowners not to cut their grass, as doing so places extreme stress on the lawn. Mowing when the temperatures reach dangerous levels can lead to heat stress, brown patches, or even kill the grass.
It is important to resist any urge to mow when temperatures reach such critical levels. You don't want to put lots of effort into lawn care over the rest of the year, only to undo all the hard work with risky mowing in summer.
You can get an all-weather iron outdoor thermometer from The Home Depot. Homeowners can stake this in a lawn and see when it is too hot to mow. Along with monitoring local weather patterns, a thermometer offers an easy way to make sensible judgements on cutting grass in hot weather.
What Temperature Is Too Hot to Mow the Lawn
When the temperatures spike during the summer, it reaches a point where it is too hot to mow, and you’d only be doing more harm than good by heading out with the mower. That critical point is when the temperature dials hit 90°F (32°C).
Taylor Olberding, the co-owner of Heroes Lawn Care, warns homeowners: ‘Do not mow your lawn if you are experiencing a huge heatwave. Once that thermometer goes above 90 degrees‚ you really need just to leave your mower in the garage․’
That advice is reiterated by Roger May from TruGreen, who says that temperatures of 90 and above ‘add stress to already compromised turf’. He tells gardeners to steer clear of mowing at such dangerous times if they want to protect their lawn in a heatwave.
‘Avoid mid-day mowing when temperatures are in the 90s, as this is when heat stress is most intense,’ the lawn expert advises. ‘The best approach is to mow during cooler parts of the day and avoid mowing during the hottest portion of the day.’
Steering clear of mowing during the scorching parts of the day and adjusting how often you mow the lawn in summer benefits both you and your grass.
Theresa Smith from NaturaLawn of America advises mowing in the early evening during a heatwave. She says: 'Evening mowing means your grass can recover in the coolest temperatures of the day.’
‘A good rule of thumb is that if it’s too hot for you to mow the lawn, it’s too hot for your lawn to be mowed,’ adds Theresa.
How Mowing in a Heatwave Damages Lawns
When temperatures reach the levels where it becomes too hot to mow a lawn, blindly heading out with a lawn mower puts additional stress on already-stressed grass. As any growth slows in extreme temperatures, it is advisable to wait until it resumes.
‘It may be tempting to head out there and get the chores out of the way‚ but you are doing way more harm than good because your grass is already completely stressed out from the heat,’ warns Taylor.
‘If you start pushing the mower across a water-starved lawn‚ the wheels and the cutting blades will literally squash the wilted blades‚ and they won't bounce back․’
He adds: ‘Every time you mow‚ you're leaving an open wound that allows the moisture to evaporate․ Your yard may end up looking like a patchwork of dead brown spots that will take forever to heal․’
If that doesn’t sound bad enough, Theresa warns: ‘Mowing during the heat of the day, especially in a heatwave, shocks the roots and makes it vulnerable to disease, which can ultimately leave you with unsightly brown spots or even kill your grass.’
The advice is clear. Cutting when it is too hot to mow a lawn will leave you with a stressed, patchy lawn.
A lawn can recover from summer heat stress once the temperatures cool and it gets some much-needed moisture. However, homeowners who heap extra stress on the grass by mowing in a heatwave may not see their lawn bounce back so quickly.
Longer Grass Is Better in a Heatwave
There may be homeowners who shudder at the prospect of not mowing for long periods during the summer. Those who love their perfectly manicured summer lawns won’t like the idea of leaving the grass taller.
But the reality is that longer grass is highly beneficial during a heatwave, as it keeps essential moisture in the soil for longer.
‘Longer grass blades can help shade the soil, meaning moisture doesn’t get evaporated from the ground as quickly in the direct sun,’ explains Chrissie Handley from Online Turf. ‘The shorter the grass, the more moisture it will likely lose, as the soil is more exposed to the sun for evaporation.’
Keeping the grass longer, which includes raising the mowing height if you do opt to cut during the cooler parts of the day, provides a valuable barrier between the precious grass roots and the harmful sun’s rays.
‘The taller the grass‚ the more shade it provides the ground under it‚ saving your roots from the heat,’ adds Taylor.
Longer grass and stronger roots make any grass more tolerant to drought. On the other hand, shorter grass means less moisture in the soil and parched roots. This makes any turf more susceptible to heat stress, weed pressure, pests, and diseases.
What to Shop
A lawn sprinkler with 16 nozzles and an adjustable watering range. It can water lawns up to 3,600 sq. ft and has a weighted base so it always remains stable during watering.
A summer lawn product that combines insect control with lawn fertilizer. It combats 15 different turf pests and keeps the grass nourished with controlled-release nitrogen.
A wetting agent helps water penetrate even dry, hard lawns in summer. This natural agent is made from Yucca schidigera to help a lawn stay hydrated in a heatwave.
Knowing the dos and don’ts of caring for a lawn in the summer months helps your grass stay healthy and looking good, rather than ending up stressed or brown. Our guide to summer lawn care has six important tasks you should be doing at this time of year to keep your grass in good shape.
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Meet the Experts
Taylor is the Co-Owner of Heroes Lawn Care, a lawn care services company. A lawncare expert, Taylor has a degree in turf and landscape management from the University of Nebraska.
Roger May, PhD, is the Director of Operations Support for TruGreen. He is responsible for providing agronomic, horticultural, and operations support on a national basis and developing innovative operational solutions.
Theresa Smith is senior vice president of NaturaLawn of America (NLA), oversees all aspects of NLA's business operations, including corporate strategy, business vendor management, marketing and more. She first started with the family business as a marketing coordinator and quickly became passionate about their mission to be environmentally responsible.
Chrissie Handley is Lawn Care Specialist providing tailored advice on laying, maintenance and general lawn care for Online Turf.
