Rescuers found the toddler Saturday, hanging upside down in her mother's car, which had flipped into a frigid Utah river a day before
If the wreck occurred when police believe it did, she may have been there for as many as 14 hours.
Lily's mother, Lynn Jennifer Groesbeck, died in the crash. She was 25 years old.
One of the biggest factors was the car seat.
Lily was in the proper car seat for her age and the seat appears to have been properly attached.
Even though the child was trapped and upside down, her body remained in the seat and above the frigid water. Doctors say that such low temperatures are dangerous, but would be even more so if the baby were wet.
Dry cold temperatures are more survivable than wet cold temperatures.
Ironically, the cold might have actually helped Lily survive, said Dr. Barbara Walsh, with the University of Massachusetts Medical School.
"She's going to have a lower heart rate. She's going to have a lower metabolism. She's going to need less sugar," Walsh said. "It's almost like the body is sort of knowing that it needs to shut down to protect itself."
A variety of other factors were also likely at play.
"We don't know what time the child was last fed, when she drank. Given that it's wintertime and she was in her car seat, she was probably wearing mittens, a hat. We tend to over bundle our children, so the fact that she was dry, she probably had on multiple layers because it's winter, and there's always a chance that she had just been sort of fed right before this happened probably all played a role," Walsh said.
A final factor may have been that the girl, as a toddler, has baby fat -- a little extra insulation. If she had been an infant, it might have been a different story.
"It's amazing. Children are very resilient, and I think sometimes we don't realize how much they actually can withstand," said Walsh.