Bob, if all I wanted to do were to stay in my RV I would agree with you. But the purpose of (at least for me) chasing 70 degrees is to be able to travel to parts of the country where the climate is most comfortable to me and see some great things along the road. There are a lot of things to see where I live in Las Vegas Nevada, but yesterday (7/7/17) it was 127 degrees in my back yard. I can tell you that it was way too hot to venture out and see anything. The official temperature in Las Vegas was only 115, but having lived here for the last 65 years, I can tell you that the official temperature is never the neighborhood temperature. The official temperature is taken at McCarran International Airport, a good 5 miles from me.
So I would really like to find a route that someone has taken that is a lot more specific than the map posted by Brian Brettschneider. It appears that in July, Denver would be a good place to be, but if you look at the average temperatures for Denver in July, they're closer to 90 than 70. So what is that dot on his map referring to since the map can't be enlarged to be able to see enough detail.