My Mother's family had resettled to the Phoenix area in the 1930's but the major influx of other people came about after the end of WWII and with the widespread adoption of refrigeration. Hundreds of thousands of GI's were brought to the desert southwest prior to and during the war. When the war ended they flocked to Phoenix and Tucson to buy relatively cheap houses and raise their families in the near perfect weather. In my Tucson neighborhood most of the families had fathers who were still in the armed forces or were war veterans.
We'd had evaporative coolers earlier but they didn't work too well during the rainy season. When A/C became popular homes and businesses moved indoors during the hot months and the annual summer migration to the cool mountains ended.
Arizona was growing so quickly that my schools from 1st to 10th grades were all on double or triple sessions. I never attended anything other than a brand new school until my family move to the Bay Area in 1960. Tucson's population in 1950 was 50,000. In 1960 it was around 200,000 and the growth hasn't stopped. Phoenix exploded even faster.