How long you can stay in a hot car depends on your age, the outside temperature and the color of your vehicle. Ideally, you don’t stay in a hot car for long as vehicles can heat up by as much as 20F in 10 minutes, representing 80 percent of the total temperature increase.
If your core temperature reaches 107F, it can be lethal and this is possible in outside temperatures of 57F or higher. Also, keep in mind that children heat up at rates three to five times faster than adults, so it’s best not to ever leave kids in hot cars, even for a short time period.