It seems a bit much to even imagine: leaving your young child locked in the car on a hot summer day, but it happens more often than you may think.

Over three dozen children die of what is called vehicular heat stroke or hyperthermia in cars. Since 1998 the number is now over 600 deaths due to this negligence.

Perhaps just as alarming is this fact: According to the Department of Geosciences at San Francisco State University, vehicular heatstroke can happen when the temperature is as low as 57 degrees, and car interiors can reach well over 110 degrees even when the outside temperature is in the 60s.

There have already been 16 reported vehicular heat stroke deaths in the U.S. this year and there were 44 last year. The Department of Geosciences breaks down these deaths even further by circumstance:

• 51 percent - child "forgotten" by caregiver (312 children)
• 29 percent - child playing in unattended vehicle (177)
• 18 percent - child intentionally left in vehicle by adult (111)
• 1 percent - circumstances unknown (6)

The highest percentage (31 percent) of the total deaths since 1998 occurs with children under 1 year of age. The worst year on record for the total number of vehicular heat stroke deaths was 2010, when 49 people died.

Here are some tips from KidsandCars.com on avoiding accidental deaths in hot cars:

• Never leave children alone in or around cars, not even for a minute.

• Put something you'll need like your cell phone, handbag, employee ID or briefcase, etc., on the floor board in the backseat. 

• Get in the habit of always opening the back door of your vehicle every time you reach your destination to make sure no child has been left behind. This will soon become a habit. They call this the "Look Before You Lock" campaign.

• Keep a large stuffed animal in the child's car seat when it's not occupied. When the child is placed in the seat, put the stuffed animal in the front passenger seat. It's a visual reminder that anytime the stuffed animal is up front you know the child is in the backseat in a child safety seat. 

• Make arrangements with your child's day care center or babysitter that you will always call if your child will not be there on a particular day as scheduled.

"On average, 38 children die in hot cars each year from heat-related deaths after being trapped inside motor vehicles," the site explains. "Even the best of parents or caregivers can unknowingly leave a sleeping baby in a car; and the end result can be injury or even death."

According to the college geosciences department, only 20 states currently have laws specifically addressing leaving a child unattended in a vehicle.