CHICAGO (CBS) — As Chicago’s weather warms up, safety advocates are warning about a deadly threat to children.

“It only takes a few minutes for your car to heat up to dangerous levels,” said David Friedman, administrator of the National Highway Traffic Safety Administration.

WBBM Newsradio’s Regine Schlesinger reports 44 children across the country died last year, after being left alone in a car on a hot day. Friedman said the numbers have been rising in recent years, but such deaths are completely preventable.

“Never leave them alone in a car. Always make sure to lock your car up and close your trunk, because some of the fatalities happen because kids themselves just get into a car and get locked in,” he said.

Tareka Wheeler, with the group SafeKids, said bystanders also play a role. If you happen to see a child alone in a car, she said “it’s so important that you take action and you call 911 immediately.”

Wheeler said parents need to remind themselves that a child is sitting in the back seat.

“Maybe they could put something on their calendar on their phone, or put their purse or briefcase or something in the back seat that they’re going to need at their final destination, just as a reminder,” Wheeler said.