Fan making a knocking noise?

Hello I have a 2000 Ford Taurus and For about two weeks Ive noticed that when my car warms up a fan cuts on and its soo loud, it literally sounds like a rabbit gone bad, or a fish tail gone crazy. When I cut the ac on it sounds like it gets faster and louder. Im really scared to drive it but its my only means of transportation. Is it dangerous to drive it for a few more days until I can get it to a mechanic, and what could it possibly be? No Smell. I did notice when the fan cuts on loud, its worse with a.c and at a stand still. At a stand still the thermometer goes up as well. but Not to the danger line at all. But when i start to move it goes down. Once my fan cuts on it does NOT cut off until I cut the car off.