John asked this question as he is very skeptical about people talking about the weather changes making them sick. He was correct to be a bit suspicous as the weather doesn’t really make us sick. There are some indirect reasons for why people are tend to be sicker when the weather changes.
First of all, when the weather is not pleasant, people spend more time inside and together which helps to spread the germs and viruses. Kids also have less outdoor recess and tend to play together in a close proximity indoors too. Also, if we dress improperly for the weather, we could stress our bodies which can slightly lower our immune system.
Also wild weather swings are more common in the spring and the fall. This so happens to also be the time of the year that allergens are high. Spring is known for tree pollen with fall more in the way of dust allergies. Therefore, people who think they get their usual cold, sinus infection or soar throat this time of the year may have very well developed an allergy. This is common as we get older.