To begin, it looks like we can finally assume that all the 100ºF days are in the books for this year. We hit 20, 1 shy of tying the all time record. I guess you can't have everything.
Las night our overnight minimum was 56ºF, still higher than the average of 52ºF, but it is likely we will have a minimum either tonight before midnight or tomorrow that is below average, which would be our first day with a below average minimum since August 2nd. August 2nd is the only day since June 23rd with a below average minimum, as illustrated nicely by the National Weather Service graphs below.
So, over the last 86 days, we have had one with a below average minimum temperature. One! That is in my view the most remarkable aspect of this summer.
Today's high will likely be near 70ºF, which will make it the coolest day since May 31, when we only eked out 69ºF. Since then, the lowest maximum temperature was 73ºF on September 14, when it was cloudy and rainy, so enjoy the cool, clear air today as it's been a while since we saw an airmass like this.