The climate of the southwest is desert climate for the most part, but in some areas with tall mountains and high elevation, it can be quite cold and snow a lot. There are different types of climates in the southwest.
In Texas, there are hot summers, and almost never rain. In the spring there will be some slightly cooler temperatures, but mostly the same as summer. In fall it is almost perfect, and it is warm but not too warm. In winter there may be a brush of snowfall, but not that much, and it will stay nice and warm outside.
In New Mexico, it is a bit colder than Texas, but not that much. Through all the seasons, it stays quite warm with some light breeze. In winter there will be snowfall, but only about half an inch of snow. It will stay warm in winter as well as summer, but towards the top of New Mexico, near Trinidad in Colorado, it will get much colder.
In Arizona it is typically warm, but not as hot as Texas would be. It is typically hot in the summer and cold in the winter like states in the west region. Last winter in Arizona, there was about a foot of snowfall, and it shocked everybody who saw it.
Oklahoma is the wettest of the southwestern states, and in spring it rains frequently, causing all the farms and crops. It is also very warm and sunny in Oklahoma, and there are hot summers and alot of refreshing wind.
The overall climate of the southwest region of the U.S. is desert climate, and it is very hot and dry on a typical day in this area.