You've probably noticed that sometimes when you're sick, you feel really hot one minute and then freezing cold the next. And to make things weirder, grown-ups keep touching your face and forehead all the time. When this happens, chances are you have a fever. A fever is when your body gets a little hotter than normal on the inside. This can mean that your body has just been invaded by germs! When germs get inside your body, your body tries to get rid of them by turning up the heat. So a fever means your body is trying to get better again!