The immune system is the body's defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.
When the humidity is high it feels oppressive outside because sweat doesn't evaporate and provide cooling. When the humidity is low you feel cooler, but your skin dries out and you get dehydrated more easily because more moisture is being evaporated from your body. The same thing applies to crops in high and low humidity. A high water vapor content is necessary to produce clouds and precipitation.
Likewise, it is difficult to study the effects of humidity and heat on breathing problems because each person handles weather differently. Someone who lives in Florida will cope with heat differently than someone who is accustomed to a cooler climate. What is certain is that heat and humidity trigger asthma, stress and heat stroke, all of which may lead to shortness of breath.