My car wont start. 1993 civic. the lights and radio come on but the engine does nothing.?

when I turn the ignition there is no response from the car. my first thought was that the gas line might have frozen. its about ten degrees in Ohio today. it has half a tank though. for the past two days the car has been having a bit of trouble starting. it kind of sounded like a pathetic chugging noise. now she wont do anything.