Myself and most people I know tend to get colds as seasons change…how come?
Colds are not caused by the weather, or by changes in the weather. Or, for that matter, by going outside with wet hair. Colds are caused by the rhinovirus, which is spread by hand to nose contact.
Yep. It turns out in cold weather humans tend to stay inside with other humans. Thid tends to increase the odds of sharing a virus.
I understand, but I can tell you for a fact that people I know and people at work get sick in numbers much larger than usual when seasons change, whether it is winter to spring, summer to fall, etc.
Entirely coincidental, as far as I know.
Well, think of the up and comming holiday too. Lots of travelers will certainly be exchanging germs.
That sounds more like allergies than sickness. Its’ easy to confuse the two. I’m sure one of our MDs will be along to sort us all out, but IMHO you’re thinking about allergies.
Well, no one I know, or have ever known, nor do I, get sick just because the seasons have changed, so maybe we all even out the law of averages?
I notice our family always gets a cold about a week after school starts - which happens to be right about when summer changes to fall. But rather than being due to the change of seasons, my theory is that the kids meet their friends and exchange all the viruses they picked up during summer vacation. Then they bring these home to mom and dad, and before you know it, the whole family is coughing and sneezing in perfect harmony 
Fall rolls around at about the same time as a new school year. Kindergarteners aren’t very aware or conscious of how colds spread: Timmy sneezes, wipes his nose with his hand, then plays with the Flintstone phone. Then Billy plays with the Flinstone phone, and later rubs his eye with his germy hands. Billy gets sick, and so do his parents. This happens many thousands of times. I’m told this is how so many people get colds every fall.
On preview, I see flodnak beat me to it. Dang.
Cecil says we don’t really know. Or didn’t, he wrote that 13 years ago.
I thought I heard a theory where it had to do with Asia and animals. Namely that during a particular time of year farmers there spent more time in contact with animals (killing them maybe?) and they picked up the latest strain which began to hit the US in the winter. Although some thing about that doesn’t seem likely.
He OP’s premise is IMO faulty.
Seasons are a human concept. Pole-ward from the tropics the weather changes from hot to cold and back every year as the Earth orbits the sun. The idea that climate has 4 phases which start and end on certain dates in entirely a human convention with no real basis in nature.
It is true the insolation and legnth of day follow (roughly) a sine curve with one complete cycle per year. And the rate of change of those two quantities is greatest at the equinoxes and least at the soltices. So those 4 points represent natural markers in the cycle. The actual weather/annual climate lags those 4 astronomical points by a large and varying amount. So the “first day of Fall” is just an arbitrary date on a calendar.
We could have chosen to have 8 seasons, or maybe just 3. In the tropics they tend to consider just 2 seasons, wet & dry.