Arizona is a western state, located in the rocky mountains, but best known for its arid climate, which is a result of its geograohy. Located between two parallel mountain ranges, it gets very little rain, neither from the Pacific nor from the Gulf. The little rain it gets originates from Pacific either as winter rain or as monsoon. However, the amount is not what you generally associate with those terms.
Located at the southern border of the United States, the climate is rather hot. But as most of Arizona is an intermontane plateau, the Colorado Plateau, the temperatures get rather cold during the night because of the height. The result are enormous temperature differences between day and night.
The major feature of Arizona's topography is the 320km long Grand Canyon, formed by a river which is fed by rains and snow melts far from Arizona, in Wyoming, the Colorado River.
About 10,000 years ago, the climate in Arizona became almost arid. So the limestone caves are definitely older and today they are generally dry and warm. In impressive example is Grand Canyon Caverns, which is dry enough that animals which die inside, are mummified.