Of more interest is how high the daily low. Being in a desert area, there are large temperature swings between the lows and highs. Midnight shouldn't be the low

Of more interest is how high the daily low. Being in a desert area, there are large temperature swings between the lows and highs. Midnight shouldn't be the low -- that would be about the hours before dawn. Basically, we're looking at a situation where the temperature had not cooled off enough during the night before the sun starts baking things again. Metro Phoenix where I live, has been having lows in the mid-90s these past couple weeks. Part of that is the heat island effect from all the asphalt, concrete, but it means even after the sun is down, we are having 100+ degree temperatures here during the evenings.