8 Summer Odors That Usually Mean There’s a Bigger Problem

Summer heat has a way of bringing out smells you’d rather not deal with—but some of those odors are more than just gross. When something suddenly starts to stink, especially in the heat, it’s often a sign that something bigger is going on.

Whether it’s rot, mold, pests, or buildup, these smells are your house waving a red flag. Ignoring them could lead to bigger repair bills down the line. Here are the ones you don’t want to brush off.

Sour Smell Around the AC Vents

If your air conditioner starts blowing a sour or musty smell, it’s not just stale air. That usually points to mold or mildew inside the ducts or the unit itself. Moisture builds up fast in the summer, especially if your drain line is clogged or your unit isn’t draining properly.

A quick filter swap might help, but if the smell lingers, it’s worth having the system looked at. Breathing in that junk isn’t good for anybody—and it only gets worse the longer it sits.

Rotten Egg Smell Outside

A sulfur or rotten egg smell near your home could be a sign of a gas leak, especially if you have propane or natural gas. That smell is added to gas on purpose to help detect leaks early.

If you smell it, don’t ignore it—especially if the scent gets stronger near gas lines or your meter. Call your gas company right away. It could be nothing, or it could be something dangerous. Better to be safe and get it checked fast.

Sewage Smell Coming from Drains

Summer heat can make minor sewer issues smell way worse. If you’re getting a sewer or rotten smell from your sinks, showers, or floor drains, that usually means a dry trap or a clog somewhere in the system.

Pouring water down the drain might fix a dry trap, but if the smell keeps coming back, you may have a venting issue or buildup that needs cleaning. It’s one of those things that only gets smellier (and more expensive) the longer it’s ignored.

Musty Smell in the Laundry Room

If your laundry room smells like damp towels even when nothing’s running, the washer might be harboring mildew. Summer humidity speeds up the process, especially if you keep the lid or door closed between cycles.

Front-loaders are known for this, but top-loaders can have issues too. Run a cleaning cycle, wipe the rubber seals, and let it air out after every load. If you smell something “off” in your laundry area, don’t assume it’s the hamper.

Sweet Smell Coming from Your Garage

A strangely sweet, syrupy odor in the garage could mean a refrigerant leak. This happens with old freezers, fridges, or even some window units if you store them out there. In high heat, the smell becomes more noticeable—and more dangerous.

Some types of refrigerants can be harmful to breathe and are definitely bad for the environment. If you notice that kind of smell, check appliances for damage or leakage. Don’t run them until you know what you’re dealing with.

Burnt Smell Near Outlets or Appliances

Hot weather already pushes your electrical system harder than usual. If you start to notice a burning plastic or smoky smell near outlets, extension cords, or appliances, something could be overheating.

It could be a bad wire, an overloaded outlet, or even a failing motor. Any one of those can lead to fire risk if you ignore it. Unplug what you can, avoid using that outlet, and get it checked before flipping it back on.

Dead Animal Smell in the Attic or Walls

Unfortunately, summer is peak season for critters getting stuck in places they shouldn’t be. If you smell something foul and can’t track it down, it could be a rodent or bird that died behind a wall, in the attic, or under the house.

The smell gets strong quickly in the heat. If it keeps getting worse or draws flies, it’s probably time to investigate. You’ll want to remove the source and disinfect the area before the smell spreads through the whole house.

Moldy Smell in the Car

If your car smells like wet gym clothes every time you turn on the AC, the cabin filter might be clogged—or moisture is building up inside the system. Summer heat combined with leftover moisture is a recipe for mildew.

Check the cabin air filter, especially if it’s been more than a year since you replaced it. You can also run the fan without AC for a few minutes before shutting the car off. That helps dry things out and prevent mold from growing in the vents.

*This article was developed with AI-powered tools and has been carefully reviewed by our editors.