This blog post was written by Katie Keating, RN, MS, patient advocate

Weather can affect most of us in general, but understanding weather forecasts is especially important for people with respiratory disorders.  My objective is to discuss a few of the different terms often used during weather forecasts and to share experiences I have had in regard to the weather. I hope that this will help you to have a better understanding of their meaning and how they may impact you as a patient. I sometimes have days when I feel awful, not realizing that it is a temporary issue due to the weather. Please note that this is my experience, but this may not always be the case and you should always contact your doctor if you are unsure.

Dew point is the first temperature at which the moisture in the air begins or would begin to collect on surfaces. Humidity refers to the saturation of the water vapor or moisture and is expressed in percentages.

A high relative humidity implies that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature and that the air is maximally saturated with water.  High relative humidity is when air is holding as much water vapor as it can. For clouds to form, and rain to start, the air does have to reach 100% relative humidity. Typically, rain falls into air with less than saturated humidity. More moisture in the air results in less oxygen to breathe and some patients may experience bronchospasm. Bronchospasms are a spasm of bronchial smooth muscle producing narrowing of the bronchi.

The following link goes to a temperature/dew point/relative humidity calculator. Although this was designed to be used to preserve artifacts, it also provides an indication for possible humidity, mold growth, etc. Dew point is the better measurement of how humid the air feels.

Heat Index is a measure of how hot it really feels when relative humidity is factored in with the actual temperature. You can use this Heat Index calculator of quantity expressing the discomfort felt as a result of the combined effects of the temperature and humidity of the air.

(Above table taken from, https://en.wikipedia.org/wiki/Dew_point).

A general rule of thumb is that when the dew point is between 60 and 70 degrees F  most  people will think it's humid. When the dew point tops 70, almost everyone will feel uncomfortably humid. High humidity reduces the effectiveness of sweating to cool the body by preventing the evaporation of perspiration from the skin.  Some NTM patients have also been diagnosed with borderline Cystic Fibrosis and do not sweat normally to begin with. The body's efforts to maintain an acceptable body temperature may be significantly impaired for normal people, never mind those with sweating disorders, resulting in a higher body temperature. With so much blood going to the external surface of the body, relatively less goes to the active muscles, the brain and internal organs. Physical strength declines and fatigue occurs sooner than it would otherwise.Alertness and mental capacity may also be affected. This resulting condition is called heat stroke or hyperthermia.

I hope that you now have a better understanding of how moisture in the air and other variables may contribute to sudden fatigue, or other respiratory issues, such as wheezing. I know that I am greatly impacted by the weather and must work around weather changes. Some of the strategies I use to cope with the change in weather include adjusting my schedule, staying in a cooler environment or shaded areas during heat waves, having nebulizers, inhalers, mucinex, water or other fluids on hand to help me deal with my symptoms. Being prepared enables you to plan your day more effectively and lessen the need for emergency care.

Perhaps, you can keep a log of tracking weather patterns and how the weather impacts you and share these findings with your doctor. This may help your doctor prescribe the right therapy to assist you throughout the challenging weather days. We cannot change the weather; however, we can change the way we deal with less than optimal weather days. 

The COPD Foundation advises that before you make any changes to your medication or therapies that you first consult with your doctor.