4. Extreme heat isn’t unusual anymore
As recently as the 1960s, summer lows still averaged in the mid-70s each night. This year, the city’s overnight lows in June, July and August fell below 75 degrees only six times.
At the other extreme, Phoenix had seven nights this summer where the temperature never fell below 90 degrees. To put that in perspective, Phoenix only had two 90-degree nights from 1895 until 1970.
In 2017, Phoenix summer-month overnight lows averaged more than 80 degrees. It was the 19th year in a row it has hit that mark.
It used to be rare that Phoenix would hit 115 degrees. Super-hot days are still uncommon, but in recent years the city has hit that level at least once each summer.
The city has had 117 days in its history where the mercury reached 115 or more. Thirty-six of them have been since 2000. By contrast, there were 36 readings of 115 or more between 1896 and 1974. There were none between 1908 and 1924.
These days, Phoenix has had at least one day of 115 degrees or more seven years in a row. This year alone, the city had six of those searing days. Only 1974 produced more: seven.
5. Hot weather starts sooner, lasts longer
Triple-digit weather isn’t limited to the summer months of June, July and August.
Between 1900 and 1950, Phoenix averaged five 100-degree days each May. Since 1990, the city has averaged nine of them.
It has also reached 100 degrees in April 53 times in the city’s history, with more than half of them since 1989. And Phoenix hit 100 degrees once in March in 1988, the only time it has done so to this point.
After-summer heat lingers more, too.
September has averaged 18 100-degree days since 1990. Between 1900 and 1925, Phoenix averaged half that many.
Phoenix has hit triple digits in October 49 times in its history. More than half of those, 33, have happened since 2003.
But don’t despair about the heat: At least it’s not next year.