I’ve just finished a three month trip driving twice across the US, hitting 21 states and camping in most of those (wife and three young kids). In summer. It’s been very hot and Big Bend was particularly brutal. We were up in the Chisos Basin the first night where it was cooler and then down near the Mexican border the second night where a storm made it bearable.

We camped in a mixed of national parks/monuments, state parks, water authority areas, BLM, etc.