Your car is one of the last places you want to encounter roaches! The good news is that heat can absolutely kill the little buggers. The bad news: it has to be really hot, and heat alone may not work.
Roaches thrive in temperatures anywhere from 15 to 120 degrees Fahrenheit (-9 to 49C). Lucky for you, if it’s even 80F (27C) out, the inside of your car can reach over 130F (54C) in just over an hour if your windows aren’t tinted. However, roaches can survive for days or even weeks at temperatures over 120F (49C) if they have a food source—or under your seat where the temperature won’t be as hot.