Cold weather doesn't actually make a person sick but when the weather is cold our bodies immune systems are weakened by the cold weather and cold temperatures and that makes it harder for our bodies to fight off infections and viruses such as the cold and flu virus.
Also the cold and flu viruses are more active in the winter and cold weather than they are in the spring and summer.
However I have gotten the flu before in both spring and summer months so it's possible to become sick even when it's not cold out.
During cold weather people are also cooped up indoors more often with the windows closed and no fresh air entering the homes and businesses they are in.
That allows people to spread cold and flu viruses much easier than they would if they were not cooped up with each other.
That's a good reason why if you have the cold or flu you should stay home until you're no longer contagious with it to avoid spreading it to other people.
You won't be very productive at work especially in an office when you are sick so it's best to stay home when possible.
Make sure you eat plenty of foods that contain Vitamin C such as Oranges, and drink orange juice, wash your hands often, drink plenty of water to stay hydrated and get your flu shot before the flu happens.