Must…avoid…New Jersey…joke…
An egg will cook once it gets to be about 160 degrees; at the very least, the egg white will be firm a that temperature. An ideal cooking surface temperature for an egg is between 250-300 degrees (which is medium to medium high on a stove), otherwise it might turn rubbery and unpleasant if it cooks too slowly. But there’s a difference between “cooking” and “cooking properly”.
The dashboard of a car can get between 180-200 degrees in direct sunlight on a hot day (ouch!).
According to the National Weather Service, the atmosphere within the car is “warmed little” compared to that of the objects within the car. A dark dashboard or a seat, for example, “can easily reach temperatures in the range of 180 to more than 200 degrees Fahrenheit,” the agency says.
That is easily hot enough to fry an egg, though again, it probably wouldn’t be the best-cooked egg you’ve ever had.