We in the upper Midwest are no strangers to extremes in the forecast. From frigid winters to hot, humid summers, we contend with a wide range of temperatures throughout the year. It means we get to enjoy the full extent of what each season has to offer, but doing so requires knowledge of how to stay safe in any weather.

The dangers of cold weather, like hypothermia and frostbite, are familiar to us Minnesotans, but there are just as many risks in muggy weather.

Below, we’ll discuss how humidity affects our bodies with help from Marny Benjamin, MD, an emergency medicine doctor at Methodist Hospital. We’ll also give you some tips on avoiding the dangerous side effects of humid summer days.

What is humidity?

There’s usually no mistaking humidity. The air can feel like it is pressing against your skin, and you might find it more difficult to move and breathe. Humidity measures the amount of water vapor, or water in the form of gas, in the air. A high level of humidity means there is a lot of water vapor in the air.

In humid conditions, the air becomes populated by hydrogen and nitrogen as well as oxygen, and our lungs have to work harder to get oxygen from the air. This is part of the reason why we feel so lethargic in humidity, and why physical activity can be especially taxing.

What is an uncomfortable level of humidity?

The National Weather Service (NWS) considers the dewpoint – the temperature the air must reach to be saturated with water vapor – the most accurate measure of how humid it feels outside.

While everyone has different comfort levels when it comes to conditions in the outdoors, the NWS generally considers a dewpoint temperature of 55 degrees and below to be comfortable. It’s when the dewpoint temperature climbs above 60-70 degrees that the air can become heavy, oppressive and uncomfortable, and your skin starts to get that sticky feeling.

Does humidity make it feel hotter?

A forecast of 95 degrees is rarely the whole story once humidity begins to rise. According to the National Weather Service heat index, 95 degrees can feel like 107 degrees with just 50% humidity. The key word here is feel. In high humidity, the temperature isn’t actually hotter, but it feels that way to us because our bodies can’t cool down. Why?

In hot temperatures, we sweat, and the action of sweat droplets evaporating off our skin cools us down. As Dr. Benjamin explains, “Sweat is one of the main ways the body cools itself. But on a humid day, sweat has a harder time evaporating into the air.” In high humidity, the air is already nearly full of water vapor and can’t hold any more.

“That’s where the hot, sticky feeling comes from. Sweat rests on our skin, unable to evaporate into the air,” Dr. Benjamin says. “As a result, our bodies continue to sweat and sweat – but feel no relief. Ultimately, high humidity throws the body into overdrive to cool itself. And with all that extra work, body temperature can rise.”

Can high humidity make us sick?

Most people agree that a hot day becomes increasingly unbearable when it’s humid out. But did you know high humidity can actually increase your risk of a heat-related illness?

“The inability to cool down leaves us more than just uncomfortable. It actually wears on our internal processes,” says Dr. Benjamin. “As our core temperature continues to rise, our bodies need to work harder to try and cool us down. This causes us to overheat.”

To stop us from overheating, the brain leaps into action, sending more blood to the skin where heat can escape (this is why warmth makes us flush) and widens blood vessels to increase sweating.

“This can lead our bodies to dehydration – losing the water, salt and chemicals that they need to function,” Dr. Benjamin says. And the diverted blood flow denies our other organs their normal blood supply. To make matters worse, these physical responses don’t work as well in humid conditions.

When our body is going haywire, we become vulnerable to a host of heat and humidity-related side effects like fatigue, muscle cramps and breathing difficulties. But it can also lead to more serious conditions, like:

  • Dehydration: As Dr. Benjamin said above, the excess sweating in extreme heat and humidity causes our bodies to lose essential fluids faster than we can replace them by drinking water. Feeling thirsty is the first sign that you’re becoming dehydrated. If you’re still not getting enough water, you’ll start sweating and urinating less, and could experience headache, stomach cramps and muscle spasms.
  • Fainting: When you faint, the blood pressure in your brain drops as blood rushes to other areas of your body to combat the heat.
  • Heat rash: Excessive sweating can lead to heat rash when sweat becomes trapped under the skin. The rash area will have raised bumps that might feel itchy and sting.
  • Heat exhaustion: The sustained loss of fluids through excessive sweating can lead to heat exhaustion. If you feel weak, nauseous or dizzy after spending time in the heat, you are likely suffering from heat exhaustion. Left unaddressed, heat exhaustion can become heat stroke.
  • Heat stroke (hyperthermia): Heat stroke occurs when the body overheats, reaching internal temperatures of 105 degrees Fahrenheit and higher. Someone suffering from heat stroke may suddenly stop sweating, have poor balance, become disoriented and confused, and lose consciousness. Heat stroke requires immediate medical attention.

How can I stay safe in high humidity?

In the Midwest, much of the summer is humid, but that doesn’t mean we can’t enjoy it. Below are a few tips for how to get the most out of the summer season without putting your health at risk:

  • Check the humidity level before venturing outside: Whatever your plans for the day, it’s always a good idea to check the weather beforehand, especially if you’re planning outdoor activities. Awareness of the forecasted heat and humidity allows you to pack enough water and sunscreen, and plan for the proper number of breaks in the shade.
  • Stay hydrated: The best way to stay on top of your hydration is to drink fluids before you get thirsty. You can pair your drink with a salty snack or choose energy drinks with sodium, as sodium helps your body retain the water you drink.
  • Consider easing up on strenuous outdoor activities: If you had planned for a long run, a hilly bike ride or a challenging hike on a humid day, consider shortening your distance, or reschedule exercise altogether (aside from swimming). Waiting for a cooler day with lower humidity will protect your health, and you’ll be more likely to actually enjoy your activity, rather than just endure it.
  • Pick clothing that breathes: Humid days are not the time to break out that tight dress you’ve been eyeing since winter. Opt for clothing with a looser fit, made from breathable fabrics like cotton and linen. Flowy clothes allow air to circulate against your skin and evaporate sweat rather than trap it. And choose cotton or linen sheets for cooler, more comfortable sleep.
  • Take a break in air conditioning: After sweating in the heat, even just a few hours in cool air can help your body recover. If you don’t have air conditioning at home, you can get some relief at your local coffee shop, movie theater, public library, museum or mall.

How to adjust to high humidity

The most important thing to do when adjusting to high humidity is to give yourself time. It takes about two weeks to adjust to a new climate. Don’t try to rush into all your regular activities without first allowing your body to acclimate in its own time.

You can increase the amount of time you spend in humid conditions a little more each day, just make sure to listen to your body.

What should the humidity be in my house?

The humidity levels inside your home should stay between 30% and 50%. Too much indoor humidity can affect your health in all the ways listed above and damage your possessions. It can even encourage the growth of mold and fungus. Too little humidity in your home and you could be dealing with dry skin and hair, frequent colds and coughs, and a breeding ground for viruses and germs.

To monitor the humidity levels at home, you can use a hygrometer, a device that measures the amount of moisture in the surrounding air. It looks very similar to a thermometer and can be purchased at hardware stores or online.

If it’s too humid at home, Dr. Benjamin recommends trying a home dehumidifier. “These are built to remove moisture from the air,” she says. And if the air in your home is too dry, a humidifier can put some of that moisture right back.

Feeling sick from heat and humidity?

It’s important to recognize when you or others are feeling more than just uncomfortable in hot and humid conditions. Don’t feel like you have to tough it out! Taking quick action to hydrate and remove yourself or someone else from the heat can prevent potentially dangerous situations.

If you or someone else is feeling unwell after spending time in the heat, our urgent care services are here to help. However, if you suspect heat stroke, call 911 immediately.