Traveling by motorhome in the United States

Too bad you cannot take your trip up the east coast this spring, Merle Haggerd is playing in Lancaster, PA on 4/28/14.

You might want to avoid the American Southwest in the summer. It can get over 100 F Arizona and/or New Mexico. I am not sure about Utah and Nevada but it gets hot enough there. Much but not all of the southwest is arid. There are nice areas in the higher elevations of Arizona and New Mexico which are up in the mountains. It doesn't get hot or too hot in the mountains.  It is a dry hear there with a low humidity. The south eastern states like Louisiana and Mississippi and the eastern part of Texas get to 88 to 96 F in the summer and it is a very humid or wet heat. I spent a year  and a half in Louisiana. There are cockroaches, aligators and many poisonous snakes in the south east part of America.
The east coast is very humid compared to the pacific or west coast of America.

It will take you 3 to 4 days to drive across the country if you don't stop to see the sites of interest.