The boy was upstairs with his 5-year-old brother watching television around 6:15 p.m. when he slid open the cracked window, pushed through the screen and fell out, Sgt. Steve Bias said.
He wandered to a neighbor's house. The neighbor saw the boy had a bloody mouth and took him back home, Bias said.
He was taken to University of California Davis Medical Center, but Bias said the worst injury was the bleeding from the mouth and there was no internal damage.
The 5-year-old brother "was so focused on the TV he didn't even notice his brother fall out the window," he said.
Police do not suspect the family was neglectful.