How to Protect a Generator from Rain and Snow

Why moisture is dangerous for a generator

A portable generator produces electricity with live terminals, outlets, and wiring. Rain, snow, and condensation can cause a short circuit, corrosion of internal components, and damage to the alternator or control panel. Water that reaches the engine intake or fuel system can also stop a generator from starting when you need it most, especially during a storm.

But the bigger danger is not to the machine. The U.S. Consumer Product Safety Commission (CPSC) states that generator exhaust contains carbon monoxide, a colorless, odorless poison that can kill you in minutes. The CPSC warns that a generator should never be operated inside a home, garage, basement, crawlspace, or shed, and it should always be used outside, far from windows, doors, or vents. That rule still holds in rain and snow, which means the protection you choose must keep water off the generator without turning its surroundings into an enclosed space.

Placement rules that keep a generator dry and safe

Place the generator on a dry, level surface. A paved area, a concrete slab, or a patio that does not flood is better than bare ground, which can turn muddy and allow splashing. If the ground is wet, put a plywood board or rubber mat underneath the generator to lift it above puddles and melting snow.

The generator must be outdoors, at least 20 feet from the house, with the exhaust pointing away from doors, windows, and vents. This distance is the recommendation from the Centers for Disease Control and Prevention (CDC), which says to operate a generator outdoors more than 20 feet from windows, doors, and vents to avoid carbon monoxide poisoning. If you cannot place the generator that far away, you are not safe just because it is under a cover; carbon monoxide can still seep into the home.

Keep the generator away from downspouts and from areas where water pools. Position it so that rain falling off the roof or blowing snow does not land directly on the control panel or outlets. If you live in a flood-prone area, place the generator on a platform that keeps it above likely water levels.

Never run a generator inside a garage, even if the door is open. The Environmental Protection Agency (EPA) warns that deadly levels of carbon monoxide can quickly build up in garages, crawlspaces, sheds, or similar areas, and can linger for hours after the generator shuts off.

Generator covers: running covers vs. storage covers

There are two kinds of generator covers, and they do different jobs. A running cover is made of flame-resistant, water-repellent fabric and is designed to be used while the generator operates. It has panels or flaps that keep rain and snow off the generator while still letting in air for cooling and letting exhaust escape. A storage cover is a heavier, more complete enclosure meant for when the generator is off, protecting it from dust, dirt, and moisture between uses.

A running cover is the safest choice if you must operate a generator during wet weather. It should fit your generator model snugly, without sagging. Make sure the cover does not block the air intake vents, the exhaust outlet, or the control panel. If the cover restricts airflow, the engine can overheat, and if it blocks exhaust, carbon monoxide can build up around the generator and drift toward your home. Follow the cover manufacturer's instructions, which usually state the minimum clearance around the generator and the correct orientation for the exhaust flap.

A storage cover is not meant for operation. Putting a storage cover over a running generator is dangerous because it can trap heat and exhaust. Use the storage cover only after the generator has cooled completely, which also protects the cover material from the heat of the muffler and engine block. Before covering a stored generator, make sure it is dry. Moisture trapped under a cover speeds up rust and corrosion, so wipe down the frame and let the generator air out in a dry area first.

Some generator manufacturers include a weather-resistant shroud or a built-in cover as part of the unit. Closed-frame inverter generators, for example, have a full housing that provides more protection from light rain than open-frame models, but they are still not waterproof. Check your generator's manual for the IP rating (Ingress Protection) of the control panel. A rating such as IP24 means the panel is protected against splashing water, but it does not mean the whole generator can sit in heavy rain. Inverter generators with a closed frame are still not a substitute for a rain cover or a shelter.

Shelters and enclosures: what is safe

A simple canopy or pop-up tent with open sides is a common shelter for a running generator. The key word is open sides. The CPSC says a generator should never be operated inside a shed, and any structure with walls that block airflow can trap carbon monoxide, even if it has a roof and a door left open. A canopy with at least two open sides allows exhaust to dissipate, but you must still keep the generator 20 feet from windows, doors, and vents.

If you want a permanent shelter, build an open-sided enclosure or buy a metal or plastic generator shelter designed for outdoor running. The shelter should have a roof to keep off rain and snow, open or louvered sides to let heat and exhaust escape, and a solid, level floor. It should be large enough that the generator is not touching any wall on any side, with generous clearance everywhere. Home standby generators are often mounted on a concrete pad with a weatherproof enclosure, and that enclosure is engineered for airflow. If you have a standby generator, follow the installation manual for clearances and do not modify the enclosure.

A portable generator should not be tied to a permanent structure that could trap heat. If you run a generator for hours during a storm, the engine and alternator get hot. Airflow is part of the cooling system. Any shelter that reduces airflow by more than a small amount increases the risk of overheating and reduces the generator's useful life.

For snow, remove heavy snowfall from the top of a canopy or shelter before it collapses. A generator cover that accumulates snow can block airflow even if it is a running cover. Brush off snow promptly, and keep the ground around the generator clear of drifting snow so that the air intake does not suck in snow, which can melt and enter the engine or alternator.

Checklist before starting a generator in wet weather

Inspect the generator for signs of moisture. If the unit got wet while off, dry the control panel, outlets, and any connectors with a cloth. Do not start a generator with wet hands or when standing in water, and do not touch outlets with wet hands. Use a ground-fault circuit interrupter (GFCI) outlet if your generator has one; this protects against electric shock in damp conditions.

Check the fuel tank and the fuel cap vent for water. Rain can find its way into the fuel cap if the generator is stored uncovered. Water in gasoline is a common cause of starting problems and can damage the carburetor.

Connect appliances with extension cords that are rated for outdoor use. Make sure the cord's plug and the generator outlet are both dry before you plug them in. If it is raining, use a small canopy over the connection point or wrap the connection with a dry cloth, but never let the cloth touch the exhaust or the hot engine.

A battery-operated carbon monoxide alarm should be working in your home whenever the generator is running. The CDC recommends installing battery-operated or battery-backup CO detectors near every sleeping area. Check the batteries before you rely on a generator for a long outage.

Ground the generator according to the manual. A wet surface can increase the risk of electrical shock, so proper grounding is even more important in rain or snow.

Running and shutting off in wet weather

If you start the generator and it runs rough, sputters, or stops, moisture may have gotten into the fuel or the ignition system. Shut the generator down and let it dry completely before trying again. Do not attempt to dry internal parts with the engine running, and do not spray water or cleaning fluid at a running generator.

When the power comes back and you shut the generator off, let it cool for a few minutes, then remove the running cover (if you used one) and inspect the generator for water that may have collected in crevices or on the frame. Dry it before putting it back into storage. If the generator will not be used for several weeks, run it dry of fuel or add fuel stabilizer, following the storage preparation procedure in the manual.

Cold weather adds another problem: ice. If rain freezes after hitting a generator, ice can form on the cover, the vents, and the exhaust. A running cover that becomes stiff with ice may not vent properly. In freezing conditions, it is better to use a shelter such as a canopy and skip a fabric cover, or to check the cover often and knock off ice before it blocks airflow.

What to pick for your use

The choice of protection depends on how often you run the generator and what kind of weather you expect. For occasional storm use, a quality running cover is the simplest option. For regular use during wet seasons, a canopy or an open-sided shelter offers more protection and better airflow. For a permanently installed home standby generator, the factory enclosure is usually enough, but you should clear snow from it and inspect the vents periodically.

Whichever option you choose, remember that a generator is never waterproof. A cover or shelter reduces the amount of water that reaches the unit, but it does not make the generator safe to submerge or to run in a downpour without supervision. Keep an eye on the weather, shut down and move the generator if conditions become extreme, and always put safety for yourself and your family above the convenience of keeping the generator dry.

If you have not bought a generator yet and you expect to run it in wet weather often, consider a closed-frame inverter generator, because its full housing gives better weather resistance than an open-frame model. An open-frame conventional generator is more exposed and needs a running cover more urgently. For long outages and whole-home backup, a standby generator installed by a professional is a more durable but more expensive solution. Match the protection to the generator, not the other way around.

For camping or RV use in wet weather, look at RV-ready inverter generators, which often have closed frames and integrated covers. Whatever you choose, always follow the manufacturer's instructions for weather protection and never block the generator's airflow.

What to pick for your use

Questions

Can I run a generator in the rain if it has a cover?

A cover designed for running generators can keep light rain and snow off the unit, but it does not make the generator waterproof. Never operate a generator in a downpour or flood conditions. Keep the generator outdoors, at least 20 feet from windows, doors, and vents, and use a shelter with open sides if the weather is severe. Follow the cover manufacturer's instructions for clearance and airflow.

Is it safe to put a generator in a shed or garage during a storm?

No. The CPSC warns that carbon monoxide from a generator can build up quickly in a garage, shed, or any enclosed space and can kill you in minutes. It is never safe to run a generator indoors, even with the door open. Use an outdoor shelter with open sides and keep the generator far from the home.

What distance should I keep between a generator and my house?

Operate the generator outdoors, more than 20 feet from any window, door, or vent, according to the CDC. This distance helps prevent carbon monoxide from entering the home. The exhaust should point away from the house and any outdoor air intakes.

Can I use a tarp to cover a running generator?

A tarp is not a generator cover. A tarp can block airflow, trap heat, and cause the generator to overheat, and it may also interfere with exhaust. Use a cover specifically designed for running generators, or an open-sided shelter that does not restrict air movement. Never let any material touch the exhaust or the hot engine.

How do I store a generator after it gets wet?

Let the generator cool completely, then dry all surfaces with a cloth. Remove any water that may have collected in the control panel or around outlets. Run the generator dry of fuel or add a fuel stabilizer according to the manual, then cover it with a storage cover that is meant for a non-running unit. Store it in a dry, well-ventilated area, but never run it there.