I took a fair amount of business trips to the California town of El Centro, which is in the desert, near the Mexican border. Average high temperatures in summer are 105/40 or more. It doesn't cool down all that much at night.
The town was settled in the early 20th Century, after the Colorado River was tapped for irrigation. Old timers told me that if you had any money, you sent the women & children to San Diego for the summer. High temperatures in San Diego in summer are about the same as low temperatures in El Centro.
Where I live, it does frequently get over 100/38 in summer, but there are usually cool, evening breezes from the southwest. The average low temp at night is about 60/15. Many older homes were build with porches or even large verandas facing south or west, so people could sit outside in the evening & enjoy the breeze. These also have large windows that can be opened at night to cool the house off.