Spring and summer bring longer days, warmer weather, and the inevitable need to maintain our properties. For many homeowners, this means regular mowing and weed trimming to keep grass manageable and reduce wildfire risk around their homes. Ironically, this well-intentioned maintenance has become one of the leading causes of wildfires during peak fire season.
Firefighters have coined a phrase for these preventable disasters: “doing the right thing the wrong way.” While property owners are absolutely correct to maintain defensible space around their homes, using the wrong equipment, timing, or techniques can spark the very fires they’re trying to prevent.
The Perfect Storm for Fire Ignition
Grass cutting equipment poses several fire risks that many people don’t consider. Lawnmowers and string trimmers can ignite fires through faulty spark arresters, metal blades striking rocks and creating sparks, grass buildup causing friction against hot moving parts, refueling hot engines, or simply setting hot equipment down in dry vegetation.
Understanding these risks is the first step toward safer property maintenance practices.
The Golden Rules of Fire-Safe Grass Cutting
Time It Right: The safest window for grass cutting is during the coolest part of the day, typically before 10 AM. This timing takes advantage of higher humidity levels and cooler temperatures that make ignition less likely.
Never Cut Alone: Always have someone present to watch for fires while you work. Two sets of eyes are better than one, and immediate response can prevent a small ignition from becoming a major wildfire.
Be Prepared: Keep fire suppression tools readily available. This might include water, shovels, or other firefighting equipment appropriate for your property.
When NOT to Cut Grass
Certain environmental conditions create extreme fire danger. Never operate grass cutting equipment when:
- Grass feels dry to the touch – Moisture content is critical for fire resistance
- Air temperature exceeds 90 degrees Fahrenheit – High heat accelerates ignition
- Relative humidity drops below 30% – Dry air quickly removes moisture from vegetation
- Windy conditions exist – Wind rapidly spreads any fire that starts and dries out vegetation
These conditions often coincide during peak fire season, which means there may be extended periods when grass cutting simply isn’t safe.
Equipment Best Practices
Choose the Right Tool: Standard lawnmowers are designed for maintained grass, not high weeds or rough terrain. For areas with tall grass or weeds, invest in a dedicated high-weed mower with string cutting capability rather than metal blades.
Maintain Your Spark Arrestor: Modern equipment should come equipped with a spark arrestor, but older equipment may lack this critical safety feature. Ensure your equipment has a functioning spark arrestor and replace it if damaged.
Replace Metal with String: Metal blades on string trimmers create sparks when they strike rocks or other hard surfaces. Replace metal blades with string trimmer line to eliminate this ignition source.
Prevent Grass Buildup: Regularly clean grass clippings from mower decks and trimmer housings. Accumulated grass against hot engines, exhaust systems, or spinning components can ignite from friction and heat.
Safe Refueling Practices: Always allow engines to cool completely before refueling, and refuel in areas clear of vegetation. Hot engines can ignite fuel vapors, and spilled fuel on hot surfaces creates additional fire risk.
Proper Equipment Storage: Never place hot equipment directly on or near dry vegetation. Allow engines and exhaust systems to cool in safe areas away from flammable materials.
The Bigger Picture
Fire-safe grass cutting requires a fundamental shift in thinking. Rather than rushing to complete yard work during convenient daylight hours, property owners must prioritize safety over convenience. This might mean waking up earlier to take advantage of cooler morning conditions, or postponing maintenance during high-risk weather periods.
The investment in proper equipment and safety practices pays dividends in wildfire prevention. A high-quality string trimmer designed for tall grass and weeds costs far less than the potential property damage from a wildfire ignition.
Making Safety a Habit
Developing safe grass cutting habits protects not just your own property, but your entire community. Wildfires don’t respect property boundaries, and a fire that starts during routine maintenance can quickly threaten neighbors and require expensive firefighting resources.
Before heading out with your mower or trimmer, check weather conditions, assess vegetation moisture, gather safety equipment, and ensure you have help nearby. These simple steps transform potentially dangerous property maintenance into genuinely effective fire prevention.
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Remember: the goal isn’t just to cut grass, but to reduce fire risk safely. When environmental conditions make grass cutting dangerous, the safest choice is often to wait for better conditions. Doing the right thing the right way protects everyone.
Download PDF from Northern Sonoma County Fire Protection District