El Paso is definitely dry -- no doubt about that. When my nieces visited from El Paso, they complained about how hot it was here in Florida. They didn't believe that it was technically 10°F cooler here until we pulled up the weather page.
But yes, I generally think that people forget that most of the Texas population lives within the effects of the Gulf of Mexico. It's fun watching the transition from green to brown when flying.
Maybe El Paso, but the rest of the state is pretty humid unless you compare it to Florida or Georgia et al.