The_science_master
The only reason why we get sick in the cold is because our body is already fighting some pathogen and when going outside without a jacket causes the internal body temp to go drastically down. As a result of this, your body now has to provide resources to get your body temp back up instead of fighting off the pathogen. This is why it seems people get sick when it is cold outside.
That is false.
When exposed to cold, the body compensates to maintain a stable core body temperature. When the body fails to do this, you develop hypothermia, at which point you have bigger issues than viruses.
The reason people get more sick in the winter is twofold:
1. The flu virus is seasonal (running from fall to spring in the US)
2. People are exposed to more during the winter.
When we try to stay indoors, the windows are all closed, kids are in school and no one's going on vacation, it's much easier for disease to circulate.