The best place in a car for your laptop is the trunk on a hot day. The trunk is a cooler part of the car, and it is not open to direct sunlight. It heats up slowly compared to the passenger area, so consider keeping your laptop in the trunk rather than the seat. Asides from heat damage, this also prevents your laptop from getting stolen or slipping when you move. Another alternative is to keep it under the front seat, which is also away from the sun’s rays.