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The Impact Of Weather Changes On Asthma.

The Impact Of Weather Changes On Asthma

As the weather changes throughout the course of a typical year, it can affect the environment around you, potentially exposing you to allergy and asthma triggers. Let’s walk through a typical year and see what we find.


Tree pollen As soon as the weather starts to warm up tree pollen season begins. Pollen can be created and released into the air even before buds appear on trees.1

How early in spring this happens, and how much pollen is created, is determined by region, tree type, and weather for each particular year. Most trees pollinate early in the morning, and wind tends to stir up pollen and transfer it. Most experts recommend watching pollen counts and staying indoors with the windows and doors closed when pollen counts are high. This is not always feasible, nor so enjoyable, so if you must open windows or go outdoors, try to avoid doing so in the early morning hours or when it’s windy.

Mold As the snow melts, it creates moisture that is good for trees, although bad for people with allergies. This moisture creates a nice breeding ground for mold spores, which can get into the air along with tree pollen, making for two potential allergy and asthma triggers during the springtime.2,3

Thunderstorms A study published in 2008 showed a three percent increase in emergency room visits for asthma on the days following thunderstorms. One theory speculates that rain causes pollen grains to rupture and get into the air, and these may trigger both allergy and asthma symptoms.4


Grass pollen Grass pollinates late spring and early summer.5

A study released in 2014 showed that it may be difficult to avoid grass pollen because the time of day grass pollinates differs from day to day based on the weather the previous day, the weather today, and whether or not it is raining. Some stop pollinating when it’s raining, and others release pollen because of rain (as discussed above). So, while experts recommend watching pollen counts and avoid going outdoors when counts are high, this may not be an easy task when it comes to grass pollen.6

Hot and humid A study performed between 1992 and 1996 showed that, for every 10% increase in humidity, the prevalence of asthma increased by 2.7%.7

Hot air has a tendency to hold more water than cold air and therefore can be heavy and harder to inhale. Humid air can also create a breeding ground for molds and fungus. These facts have inspired asthma experts to recommend keeping the humidity in your home less than 50% for easier breathing. This can be accomplished with a dehumidifier and air conditioning.8

Ozone It usually exists in a layer about 20 miles above the earth’s surface, and amounts on the surface are usually negligible. All winter long we look forward to heat from the sun. However, sunlight can mix with pollution from factories, power plants, and vehicles to cause ozone on the earth’s surface. In large cities, ozone can become a major component of smog, which can trigger asthma. Various studies have also shown that ozone itself can trigger asthma.9,10


Ragweed It begins to pollinate in mid-August and continues to pollinate through October, or until the first frost. Like tree pollen, ragweed pollen is highest in the morning hours and when it is windy. 11,13

Mold Dead and decaying leaves can create a breeding ground for molds. And, unlike the pollen season, the mold season does not end with the first freeze, as mold spores are resistant to freezing temperatures. For this reason, it’s important to wear a mask if you rake leaves, or to find someone else to rake leaves for you. This is true even if it is freezing outside.14,15


Cold air Cold air can irritate airways in such a way as to cause asthma symptoms. This is especially true when you exercise in cold air. If you must go outdoors, you can wear a scarf over your mouth and nose to help warm and humidify inhaled air. It’s also a good idea to exercise indoors during the winter months.

Winter colds It’s a common fallacy that colds are caused by cold weather. However, you are more likely to catch a cold during the winter mainly because you are more likely to spend your time in warm indoor environments with the windows and doors shut, an ideal environment for viruses and bacteria to spread from one person to another.

The best way to avoid getting sick is to get your flu and pneumonia shots, wash your hands often, take your vitamins, get plenty of sleep, and drink plenty of water. Keeping your home well ventilated is also a good idea.16 The single most important method of preventing colds is to wash your hands a lot.

So, how do I hide from these seasonal allergy and asthma triggers? Good questions. It’s not easy. But just being aware of potential allergy and asthma triggers is a good start, and try to avoid them as best you can. If you continue to have symptoms, you should work with your doctor on developing a plan of action.

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. Flowering Habits of Trees and Shrubs - Arnold Arboretum. Accessed November 12, 2016.
  2. Science of the Seasons: Snow melts, mold remains. The Mouth of The Kenai. Published 2010. Accessed November 12, 2016.
  3. Matheny, Cards reach terms. CBCNEWS. Accessed November 12, 2016.
  4. ScienceDaily. ScienceDaily. Accessed November 12, 2016.
  5. By visiting the office of an allergist, you can expect an accurate diagnosis, a treatment plan that works and educational information to help you manage your disease and feel better. Outdoor allergens TTR | AAAAI. The American Academy of Allergy, Asthma & Immunology. Accessed November 12, 2016.
  6. A. Scientists map the worst times of day for people allergic to grass pollen. EurekAlert! Accessed November 12, 2016.
  7. Weiland S, Husing A, Strachan D, Rzehak P, Pearce N. Climate and the prevalence of symptoms of asthma, allergic rhinitis, and atopic eczema in children. Occupational and Environmental Medicine. Published 2004. Accessed November 12, 2016.
  8. The relationship between house dust mite growth and relative humidity | AAAAI. The American Academy of Allergy, Asthma & Immunology. Accessed November 12, 2016.
  9. Brasier, Allan R., editor, “Heterogeneity in Asthma,” 2014, Springer, pages 56-57
  10. Health Effects of Ozone in Patients with Asthma and Other Chronic Respiratory Disease. EPA. Accessed November 12, 2016.
  11. Why Fall Makes Us Sneeze. NBCNEWS. Accessed November 12, 2016.
  12. Ragweed plants packed with pollen. documents/libraries/el-ragweed-patient.pdf. Accessed November 12, 2016.
  13. What's Ragweed and Why Is It Giving Me Allergies? Verywell. Accessed November 12, 2016.
  14. Molds. Molds. Accessed November 12, 2016.
  15. AAFA. Mold Allergy. Accessed November 12, 2016.
  16. Ten ways to avoid colds and flu this winter. Daily Mail. Accessed November 12, 2016.