Humidity Doesn’t Just Make You Feel Gross. It Can Harm Your Health, Too Key Takeaways

• Humidity is the concentration of water vapor in the air. In humid conditions, sweat struggles to evaporate from the skin, making it harder for your body to release heat effectively and cool you down.
• High levels of humidity combined with heat and other factors can lead to symptoms like dehydration and muscle cramps and increase the risk of heat-related illnesses like heat exhaustion or heat stroke.

• To cope with humidity this summer, experts recommend staying hydrated, wearing light-colored clothing, and avoiding the sun during peak hours.
As summer approaches and temperatures begin to rise across the United States, it’s crucial to be aware of how the weather can affect your health as you plan your activities. While you probably know to be on alert for hot weather, another factor you may not think of but that is very important is humidity.
It might seem like having a little water in the air would be helpful on a sweltering summer day, but the meteorological reality is a little more complex than that. High humidity levels combined with elevated temperatures can create a dangerous mix, Kevin Lanza, PhD, assistant professor at UTHealth Houston School of Public Health, told Verywell.

“Humidity in and of itself is a lesser threat, at least at lower temperatures, but if you’re coupling that with higher temperatures, with hot and humid conditions that’s when you’re potentially in trouble,” said Lanza.
Here are the most important health effects of humidity that you should be aware of.
When Is Being Outside in Humidity Unsafe?
What’s considered an unsafe high humidity level varies depending on the individual, Shashank Ravi, MD, clinical assistant professor in emergency medicine at Stanford Medicine, told Verywell.

Specific factors, like your hydration level, how long you’re exposed to high humidity, and how much you exert yourself in these conditions, all play into how it affects your well-being. And it’s not just when you’re outside, either. “Being indoors in high humidity without circulating air can also be dangerous,” said Ravi.
In general, when humidity levels are high—above 60%–۷۰%—it can make sweat evaporate from your skin more slowly. That, in turn, makes it harder for your body to cool itself, David Cutler, MD, a board-certified family medicine physician at Providence Saint John’s Health Center in Santa Monica, CA, told Verywell.

Inefficient sweating in high humidity “can make people feel hotter than the actual temperature,” said Cutler. “High humidity also increases the heat index, which is the perceived temperature. For example, an actual temperature of 90 degrees Fahrenheit can feel like 105 degrees Fahrenheit if the humidity is high.”
On the other hand, low humidity levels—below 30%–۴۰%—can also negatively affect your health by causing dry skin and respiratory discomfort. “Low humidity can dry out mucous membranes in the nose and throat, leading to irritation, coughing, and increased susceptibility to respiratory infections,” said Cutler.

How Does Humidity Affect Your Health?
Humidity’s effect on the human body and your health really depends on how the level interacts with temperature, according to Lanza. While humidity by itself may not pose a major threat—especially at lower temperatures—its effects can be serious when combined with heat.
Therefore, high humidity can lead to health concerns and even make individuals “more susceptible to health risks like dehydration and fatigue,” added Ravi.

Here are just a few things that can happen when you’re dealing with high humidity and heat:
• Dehydration: High humidity levels can lead to excessive sweating and cause the body to lose fluids faster, according to Ravi. If hydration levels are not replenished quickly, it can lead to dehydration and symptoms such as fatigue, dizziness, and confusion.
• Skin irritation: Humid conditions can cause skin irritation, such as heat rashes and even fungal infections, when there’s prolonged exposure to both heat and moisture, according to Lanza. High humidity can also make the skin oily and worsen conditions like acne, added Cutler.
• Muscle cramps: In humid conditions, people may lose too many electrolytes, which can shock the muscles and lead to cramping in the arms, legs, or abdomen, according to Lanza.
• Worsen respiratory conditions: High humidity can exacerbate respiratory conditions like asthma and allergies by promoting the growth of mold, dust mites, and bacteria, according to Cutler.
• Heat exhaustion and heat stroke: High humidity can increase the risk of serious heat-related illnesses such as heat exhaustion and heat stroke because the body’s cooling mechanism is less effective, according to Cutler. When the body can’t regulate its own temperature and starts to overheat, it can cause organ damage or even failure.