Watch the Sky by Kirsten Hubbard

Jory's family lives just outside of town, and they're a little strange. His stepfather holds frequent drills in the middle of the night, so the family will be ready for some unknown emergency. His little "sister", Kit showed up in the backyard one day and hasn't said a word in three years. The stepfather says a meteor shower is the sign he's been waiting for, so he has the family start digging a shelter into the base of the canyon. He won't tell the family what the danger might be, but he says the family needs to trust him. No one can find out what they're doing, and no one can find out about Kit. Jory makes some friends when he returns to public school, but that only makes it harder to keep secrets. Jory wonders if his stepfather is wrong; what if there is no danger coming? But what if he's right.

The plot is a bit unusual. The stepfather is certain that something is going to happen, and he's sure he sees signs of the impending disaster. He looks to the skies when he talks about it, but he won't the danger is aliens. Jory's character is put in a tough spot. He wants to be a faithful son, so he helps prepare the shelter as best he can. However, he likes going to the public school and making friends. Kit is a mysterious character, and Jory discovers a secret about her. I wish there had been more of a resolution to the book, because I'm left with many questions about the family's survival.