Investigators say his mother, 26-year-old Nicole Carmon, got into an accident overnight then left her auto with her child inside.
Authorities started looking for her son at 10.40am Saturday.
A 2-year-old boy was left in a vehicle during subzero temperatures Friday night in Thornton.
So far, the boy's condition has not been released. The babysitter called police.
A two-year-old boy who was left inside a vehicle overnight as temperatures plummeted well below zero in Thornton was found miraculously alive by police late Saturday morning.More news: CDC issues Texas city warning for pregnant women after Zika
Police were looking for a 2013 green Ford Fusion that may have been involved in a crash, and when they found the auto they spotted a little boy inside.
Police told the Denver Post that Carmon told Westminster police she was involved in a Friday night auto accident and left the toddler inside the vehicle.
Officers reportedly found the child in a parked vehicle outside of a strip mall in Colorado on Saturday afternoon. At the time, it was thought the auto had been involved in a crash either late the night before or earlier that morning and that a child had been left in the vehicle. The boy was found in a auto seat, half buckled in the back seat.
Carmon was scheduled to appear in court Monday morning.
Barnes said, according to KDVR: 'Police are investigating the circumstances that led up to the child being left alone inside the vehicle and how long the child was left alone'.