Yes, 64 percent humidity is high. The EPA recommends keeping indoor relative humidity between 30 and 50 percent and says it should never exceed 60 percent. At 64 percent, you’re above that ceiling, which means increased risk of mold growth, dust mite problems, and general discomfort.
Why 60 Percent Is the Cutoff
The 60 percent threshold isn’t arbitrary. Above that level, moisture begins condensing on cooler surfaces like windows, walls, and pipes. That condensation creates the damp conditions mold needs to colonize. The EPA specifically notes that relative humidity above 60 percent is likely to cause condensation in buildings, which leads directly to mold growth.
Dust mites also thrive in this range. These microscopic creatures need humidity above 40 to 50 percent to survive, and their populations increase substantially as humidity climbs higher. Their waste particles are small enough to become airborne and are one of the most common triggers for asthma and allergies. At 64 percent, you’re giving them a comfortable home.
How 64 Percent Feels
Whether 64 percent humidity feels uncomfortable depends on context. Outdoors, the National Weather Service uses dew point rather than relative humidity to gauge comfort, because relative humidity shifts with temperature throughout the day. A dew point between 55 and 65 degrees Fahrenheit already feels sticky with muggy evenings. Above 65, the air feels oppressive. So outdoor humidity of 64 percent on a hot day can range from mildly uncomfortable to miserable depending on the actual moisture content of the air.
Indoors, 64 percent consistently feels damp. You may notice a clammy sensation on your skin, fabrics that feel slightly moist, or a general stuffiness in the room. Bathrooms and basements are the most common places to hit this level, but poor ventilation or a lack of air conditioning can push entire homes above 60 percent during warm, humid months.
Effects on Sleep
High humidity disrupts sleep in measurable ways. It increases wakefulness during the night and reduces the time you spend in both deep sleep and REM sleep. These are the two stages your body relies on for physical recovery and memory consolidation, so losing them has real consequences beyond just feeling groggy. Humidity also causes excess sweating, which makes lying in bed uncomfortable and can lead to frequent tossing and repositioning. If your bedroom regularly sits at 64 percent or higher, your sleep quality is likely suffering even if you don’t realize it.
Risks to Your Home
Mold is the most obvious concern. It can grow on drywall, ceiling tiles, wood, carpet, and insulation once moisture levels stay elevated long enough. You won’t always see it right away, since it often starts behind walls or under flooring where condensation collects.
Wood flooring is particularly vulnerable. Sustained humidity above 60 percent can cause planks to absorb moisture and warp upward, a problem known as convex warping. The recommended range for preserving wood floors is 40 to 60 percent relative humidity with a minimum temperature of 15°C (59°F). At 64 percent, you’re outside that safe zone, and if the elevated humidity persists for weeks, the damage can become visible. The good news is that warping caused by humidity fluctuations can often be corrected by bringing moisture levels back down with a dehumidifier.
How to Bring It Down
A dehumidifier is the most direct solution. For a room where humidity sits in the 60 to 70 percent range, Consumer Reports recommends a 20-pint unit for smaller spaces (up to about 500 square feet) and a 30- to 50-pint unit for larger areas. If you run a dehumidifier at full power and can only get down to 60 or 70 percent, the unit is too small for the space.
Beyond dehumidifiers, a few habits make a significant difference. Run exhaust fans while cooking and showering. Make sure your dryer vents to the outside, not into a garage or crawl space. Keep air conditioning running during humid months, since it naturally pulls moisture from the air as it cools. If you have a basement that stays damp, check for water intrusion around the foundation before relying solely on a dehumidifier to compensate.
A simple hygrometer (available for under $15 at most hardware stores) lets you monitor your indoor humidity in real time. Place one in your bedroom and one in your most problem-prone area, whether that’s a basement, bathroom, or laundry room. Your target is 30 to 50 percent, with 60 percent as the absolute maximum. At 64 percent, you’re not drastically over the line, but you’re far enough past it that mold, dust mites, and comfort problems will develop if the level stays there.