Question on rear facing

Anne 💙💙💙 • Mom to 3 boys. August 2015, December 2016, December 2018

Our 15 month old is rear facing. In July we are headed to VA to visit family. Last year when we did this he got so hot because he was rear facing and the cool air just didn’t seem to get back there. How do you keep your rear facing babies cool??? The sun was just beating down on him so bad. We bought those car shades but they didn’t work very well.