Why are my car's brakes so stiff in the morning/cold?

I'm not sure if it's because it's the morning or because it's cold, but whenever it's either one or both of those factors, my brakes are very touchy. Like I press down on it lightly and the whole car stops suddenly and then when I release it jerks back, making it a very jerky, stiff, and rocky experience. It only happens for a short while before it becomes smoother. What is the explanation for this phenomenon? via /r/cars http://ift.tt/2tPZLyp