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humidity and asthma

What is the Connection Between Humidity and Asthma?

Weather, any time of the year, is not a friend to people with asthma. But hot, humid days can be some of the most challenging weather conditions we have to contend with.

Have you noticed that your breathing gets worse on days when the humidity rises over 50%? If so, you’re not alone.

I know that during the 30 years I lived in southern New Jersey, my asthma was definitely a lot worse than it’s been in the 3 years I’ve lived in southwestern Colorado. New Jersey, right on the Atlantic coast, has much higher humidity levels than the high desert and mountains of my current home. I especially felt the effects of heat and humidity during the summer allergy season.

Understanding humidity and asthma

In the simplest terms, humidity is the amount of water or moisture in the air. When the media talks about humidity levels, they’re referring to what is known as “relative humidity.1” This is the percentage of water in the air, compared to the maximum amount of water the air can actually hold at the current temperature. Hot air can hold more moisture than cold air. So, a relative humidity level of 70% on a hot day is going to feel a lot “wetter” than the same humidity level on a cold day.

According to the National Weather Service, humidity during hot summer months of less than 55% is “comfortable.” 55 to 65% humidity begins to feel “sticky,” and anything over 65% is “oppressive.2” You can expect that humidity becomes an irritant type trigger for many asthmatics at levels of 65% and higher.

How humidity affects asthma

There are a few ways in which heat and humidity can affect breathing in people with asthma:

Hot, humid air is harder to breathe in

Moist air feels heavier and denser. Hot outdoor temperatures seem to magnify this effect.3

Humidity can activate sensory nerve fibers in the airways

These C-fibers are thought to narrow the airways and stimulate coughing.4

Hot, humid conditions provide the perfect breeding ground for asthma allergens

Dust mites, mold, and pollen are all common triggers for people with allergic asthma. Those allergens love hot, humid conditions.3

Heat and humidity raise ozone levels

Ozone is the culprit in air pollution. Humidity makes the air stagnant, trapping pollutants such as car exhaust, as well as pollen and mold spores.3

In addition, extreme changes in temperature can be a trigger when you have asthma. Think about what a shock it can be when you walk out of a cold, air-conditioned building into suffocating outdoor heat.

Hot, humid indoor air can also make it harder to breathe.

Actions you can take to maintain asthma control

People with asthma are more likely to have asthma flare-ups, or exacerbations, during hot, humid conditions. In fact, a study done by researchers at the Children’s Hospital of Michigan found that with as little as a 10% rise in humidity, there was an increase in hospital visits for asthma. The same held true for every 10-degree rise in atmospheric temperature5 (They determined this by examining more than 25,000 hospital emergency department records).

So, if you’re living in hot, humid weather conditions, it’s important to be vigilant about your asthma control.

How to protect your asthma from humidity

First of all, every person with asthma, whether child or adult, should have a written Asthma Action Plan that will guide you in maintaining your asthma control. As soon as you notice any symptoms starting or worsening, refer to your action plan. But beyond that, here are a couple of other suggestions.

Check the air quality daily before going outdoors

Find out what the outdoor temperatures and relative humidity are. Check the local pollen and mold levels. When any of those factors are high, your best bet is to stay indoors in air conditioning as much as possible. Exercise indoors or at times of day when temps and humidity are lower.

Use your asthma medications

Be sure to take your controller medicine daily or twice daily as prescribed. Also, always keep your quick-relief/rescue inhaler on hand wherever you go, should symptoms crop up.

How have hot, humid summer weather conditions affected your asthma? Let us know in the comments or share your story here.

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. National Geographic. Humidity. Accessed August 2019.
  2. National Weather Service. Dew point vs humidity. Accessed August 2019.
  3. Asthma and Allergy Foundation of America. 3 ways humidity affects asthma. Accessed August 2019.
  4. D Hayes Jr, PB Collins, M Khosravi, R Lin, L Lee. Bronchoconstriction triggers by breathing hot humid air in patients with asthma. American Journal of Respiratory and Critical Care Medicine. 2012;185(11):1190-1196. doi: 10.1164/rccm.201201-0088OC
  5. N Mireku, Y Wang, J Ager, RC Reddy, AP Baptist. Changes in weather and the effects on pediatric asthma exacerbations. Annals of Allergy, Asthma & Immunologyst. 2009;103(3):220-224. doi: 10.1016/S1081-1206(10)60185-8


  • Davo
    2 mins ago

    Hi,fires are finally finished ,here in Australia where I live it very wet hot and humidity is usually between 70 92 % I’m finding it really hard to cope with overlap asthma ,I’m 66yrs old , inhaler s seem to only help so much ,drs don’t seem to have any solutions ,really need it to dry up,was only few weeks ago we needed rain to stop fires an smoke ,air con sounds good but can cause problems with my breathing , portable air con doesn’t help much , dehumidifier seemed ok at first.oh well just gotta handle it,has anyone noticed bloating or numb feet with there asthma .when it’s warm or humid ,thanks take care everyone.

  • smallrain
    3 weeks ago

    Right now I live in a very rainy place in the winter. It seldom goes below freezing or snows. I find it difficult breathing in this type of atmosphere. A while back it did freeze and we had dry snow. The humidity dropped and I felt better. Back to rain now.

  • Leon Lebowitz, RRT moderator
    3 weeks ago

    Hi smallrain, and thanks for joining in this conversation regarding humidity and asthma. We appreciate you sharing your particular situation with the community. We are grateful for your input.
    All the best,
    Leon (site moderator

  • Septsong36
    4 weeks ago

    When the humidity is higher then the temp outside. I loose my voice, not completely but very raspy. I don’t go outside but it still happens to me inside. Then the coughing starts. I’m very tired of having asthma. It does control my life. On Christmas eve my daughter and I have our tradional supper and then go out to see the Christmas lights. This year it was raining and the humidity was high. We did nothing except eat some tamales and pasole. Very boring evening.

  • rjmoon
    6 months ago

    When I’m outside in high humidity, it feels like I’m breathing with a warm, damp washcloth over my nose and mouth. Today the humidity was in the low 70’s, and I just stayed inside in the air conditioning. I’m getting over a mild flare-up and it just wasn’t worth going out. But we had a heavy rain earlier this evening and it is much cooler and more comfortable now, so I got to spend some time outside after all 🙂

  • DN11
    5 months ago

    Hi rjmoon, I can relate to you as I also tend to get shortness of breath when outside and hot weather makes it a lot worse. Glad you had rains. Removes that suffocating feeling and able to enjoy the outdoors.
    I am prone to asthma symptoms when exercising outdoors—walking, biking etc. Shortness of breath mainly. Currently I am working with researchers in a study that monitors environmental pollutants withing one’s breathing zone. This is interesting to me as it could help determine outdoor triggers that cause this shortness of breath. I’m hoping this helps narrow down the root cause. I would love to see if anyone else here thinks of the environmental pollutants are causes for their asthmatic symptoms.

  • Lyn Harper, RRT moderator
    6 months ago

    Hi rjmoom – I’m glad you have a cool place you can be in when the humidity is as high as that. You describe it well; it is like having a warm, damp washcloth over your face. I hope today is a better day and you’re able to get out if you want to.
    Lyn (site moderator)

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