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Q: I’ve seen a neighbor mow the lawn in the morning shortly after they turned off the sprinklers. I thought it wasn’t a good idea to cut grass when it’s wet. What’s the word on mowing wet grass—yay or nay?
A: While there are some conditions under which it’s acceptable to mow grass when it’s wet—from sprinklers, rainfall, or morning dew—generally speaking, you’re right. The timing is ill-advised, and here’s why.
Water and electricity don’t mix.
Using an electric lawn mower on wet grass, especially with an extension cord, runs the risk of electric shock. When the connections (and any wiring within worn or damaged portions of the cord) are exposed to moisture, it can lead to damage to the machine—and electrocution to the operator.
Even if you’re using a gas-powered lawn mower, rainwater might get into the fuel tank. This can cause the engine to malfunction and stop working altogether. Over time, water can cause corrosion of engine parts, leading to expensive-to-repair damage.
Cutting grass in the rain poses a personal danger.
Aside from the risk of electric shock, simply walking across a slick lawn can be dangerous. “It can be unsafe for you as the mower operator because wet grass can be slippery, increasing the risk of slips and falls,” says Chandler Moncada, who works with CGL Landscaping in Phoenix.
You certainly don’t want to fall anywhere close to the lawn mower blades. You could also take a tumble in wet weather and hit your head on that beautiful stone edging you just installed, or on the adjacent driveway.
Heavy rain could impair your ability to see what you’re mowing and where you’re going. If you wear eyeglasses or safety goggles, cutting grass in the rain could cause the eyewear to become fogged up or coated in water, further diminishing your ability to see clearly.
Damp blades of grass can damage the mower.
Without the appropriate fuel stabilizer, leftover fuel in the mower’s gas tank can be contaminated when cutting grass after rain because of excessive moisture and even corrode your machine.
“Mowing wet grass can put extra strain on the mower’s engine and blades,” says Moncada. “Wet grass is heavier and can clog up the mower deck, leading to decreased performance and potential damage to the mower’s components.” Blockages force the machine to work harder until it shuts off if you’re not carefully cleaning as you go.
It’s almost impossible to get an even cut when grass is wet.
Wet grass blades are slick and tough to slice, creating an uneven shred (at best), which is yet another reason not to mow the lawn when wet. Mowing wet grass “can cause the grass to tear rather than being cleanly cut,” says Moncada. Additionally, wet grass clumps together, making it harder for the lawn mower blades to cut through thick clumps, meaning you end up with a raggedy mess. The wet, soggy ground a mower encounters when mowing after rain is more likely to allow grass to be pulled up out of the ground entirely by dull mower blades rather than being cleanly cut by the blades.
Sharp mower blades will make the job easier, though.
If you absolutely must mow your wet yard—the Queen is on her way over for a visit, perhaps—make sure your mower blades are in peak condition, either newly sharpened or recently replaced. (In general, lawn mower blades should be sharpened at least twice per season, or after 25 hours of use.) If they are less than scalpel-sharp, you might need to make two or three passes over the same patch of wet lawn to get even a fraction of the cut you’d get if the lawn were dry. And you definitely don’t want to be toiling in the yard when Her Majesty rolls up!
Mowing a wet lawn is an easy way to spread fungal disease.
“Mowing wet grass can be harmful to your lawn,” says Moncada. Being torn rather than cut “can stress the grass and make it more susceptible to diseases,” he adds. Because fungus thrives in wet environments, it shouldn’t come as a surprise that conditions such as brown patch disease can develop on a lawn that’s been cut right after a rainstorm. When you leave clumps of damp, matted clippings on the lawn without sufficient airflow to dry them out, the grass becomes more susceptible to fungal diseases. The wet grass clippings that stick to the underside of the mower deck can grow mold, too, which can be spread to your lawn the next time you mow.
Cutting wet grass can damage the ground.
Aside from the potential spreading of fungal diseases, cutting grass when wet can damage the soil. Mowers are heavy machines and are not designed for use on soft, muddy ground. The mower’s wheels (and even your shoes) can compact saturated soil or even cause ruts to form, damaging roots and hindering the growth of healthy grass in the future. Always check the soil before firing up your lawn mower. If it looks muddy or feels soft, it’s probably better to wait on cutting the grass.
Mowing a wet lawn results in extra cleanup.
Grass clippings get extra clingy when they’re wet, so mowing grass when it’s wet requires extra cleanup. The damp grass clippings that stick to a mower’s undercarriage can create a breeding ground for mold—and eventually a busted mower—if the machinery stays too moist for too long.
Be sure to scrape the deck clean of those stuck-on blades, brush off the tires, and wipe down the body of the mower. Then, turn your attention to the stains left behind. Chlorophyll in freshly cut wet grass will cause more stains than what you incur on an average mowing day, so be prepared to remove grass stains from your clothes, shoes, and driveway right away.
Set the lawn mower deck height to a high setting for the most even cut.
Finally, change your mower deck to one of the higher settings to cut blades to 3 or 4 inches long and no shorter. It’s tough for a lawn mower to get a close shave when mowing when grass is wet, so cut it some slack if you want it to do its job as well as it can. Following these simple rules of thumb can keep you safe even while trying to keep up with lawn care in less-than-ideal conditions.
If you have to mow wet grass, use side-discharge mode so wet grass doesn’t damage your lawn mower bag.
Before mowing a wet lawn, ensure that you take all of the safety precautions. First, test the soil’s saturation. When standing on your lawn, you should not be able to sink into it or see water rising around the edges of your shoes—mowing through so much water is a bad idea. Without the presence of standing water, you could potentially tame your yard to some degree using a stabilized gas-powered mower with sharp blades.
If you can, set your mower to side-discharge mode. Though this leaves rows of cut grass on your lawn for manual bagging later, it will save you the mess of dealing with a mower bag with a wet interior. You could also try pulling Grandpa’s reel mower out of the shed—you might have the best luck with it on wet grass.
FAQs
When dealing with mild morning dew on the grass or after light rain showers, you may only need to wait between 2 and 5 hours for the lawn to dry before mowing. With a heavier rainstorm, you should wait at least one day to mow safely. Shady areas of the lawn will take longer to dry than those in the sun.
While wet grass alone may not dull a mower blade, its slick surface certainly doesn’t make the cutting process easier. And if left to sit on the blade, the saturated clippings could cause rust and an early demise to metal mower parts such as the blade.
The best time to cut grass is somewhat dependent on where you live. If your mornings are dewy, and your afternoons are hot, mow during that sliver of time mid-morning when the dew has dried but before the sun is scorching. If morning dew is only something you read about in sonnets, and it gets hot before breakfast is even on the table, the best time to cut grass is in the early morning.
Final Thoughts
While it might be tempting to mow your lawn as soon as the rain clears, you’re better off waiting until the grass is dry. Cutting wet grass can lead to plant fungal diseases, soil damage, and even mower operator injury—all of which are preventable with a little patience.
