It's just one asteroid, John, not a meteorite shower. It's got the power of an H bomb, so a steel helmet might be more appropriate.
However, it will not penetrate the atmosphere. But from my experience of the Web, people will be making all sorts of weird predictions.
I already know them off by heart: the poles will invert, there will be big waves, Burlington House will come down... , but fortunately there will be December 21st before that! Ahem
