But it's dry in Phoenix and the temps drop at night right?
It's usually very dry, but summer is also
monsoon season and after a monsoon thunderstorm, it can easily be 110+ and incredibly humid as all that rain evaporates back into the air. As mentioned before, the lows are in the high 80's or low 90's. It's not unusual to be over 100 degrees at 9pm.
Three things:
1) I always love these "I can't believe what another region thinks is ____." The issue is what the area is used to and what they're prepared for. DC apparently has an average snowfall of about 15" (which seems high to me). A foot of snow all at once here may seem like nothing to someone from up north, but this area isn't prepared for it so everything shuts down.
2) The humidity here, at 12:30am last night, was 78%.
3) I know people from Phoenix, and they all say that in the summer you tend to go from house to car to office, and always stay in the AC
1) True. Everyone's used to it there so it's pretty normal.
2) See notes about monsoon season above.
3. Also true. We used to start our car 15 min. before leaving to allow it to cool down. It can easily get hot enough to burn your skin. Also have to remember to bring the car seats inside so that you don't sizzle your kids (if you don't have a garage). The outdoor shopping areas have misters installed that really help because it's so dry, the evaporative effect can cool the air 10 degrees or more. People in Phoenix suffer through the 4 months or so of barely tolerable weather because it's absolutely wonderful the rest of the year.