Think that you might have accidentally pressed the DISP or DISPLAY button on the back of your camera. This manually turns the LCD display on and off to save batteries. You would then use the optical viewfinder in its place. To turn the screen back on, just press the DISP button one more time.
But if you've already tried this, have you also tried downloading any of your photos taken with the black screen to your computer? Are the photos also black? If so, you might instead be experieincing a stuck shutter (possibly due to the cold weather).
A stuck shutter is another common failure mode for digital cameras. The symptoms of a stuck or "sticky" shutter are very similar to CCD image sensor failure. The camera may take black pictures (for shutter stuck closed), or the pictures may be very bright and overexposed, especially when taken outdoors (for shutter stuck open).
To confirm a stuck shutter, put the camera in any mode other than "Auto", and turn the flash OFF (you don't want to blind yourself for the next step). Next look down the lens and take a picture. You should see a tiny flicker in the center of the lens as the shutter opens and closes. If no movement is seen, then you likely have a stuck shutter. If so, please see this link
for further info and a simple fix that may help.