Phoenix officially hit 80º for the first time this year on Feb 2nd, which is only one day earlier than the 30-year average of Feb 3rd (based on 1981-2010 data). But the comment alway comes up: it feels like it is getting earlier every year.

So... is it? Let's go to the data!

Before we get started, it should be noted that weather observations go back to 1896 in Phoenix. The weather station moved around to a few locations in Central Phoenix from 1896 to 1953. From 1953 onward, it was located at Phoenix Sky Harbor but has moved locations there three times (1953-1994, 1994-2000, and 2000 to present).

Ok, now that we have that out of the way, the graph above depicts the 30-year rolling average, from 1925 to 2021, for the first day Phoenix has recorded 80º+. It also displays the 10-year rolling average to show a bit more detail.

It is quite apparent that yes indeed, based on the 30-year rolling average, the first 80º+ days is getting earlier. In 1925, the average first 80º+ day was Feb 21st, and in 2015 the 30-year rolling average came in at Feb 1st. The 30-year rolling average with this year plugged in comes out to Feb 3rd. (Note: these dates were converted from truncated Julian day)

These data also show that the overall trend is beginning to flatten out, especially compared to the late 1980's into the 1990's.

Will this trend continue? We shall see in the coming years as data comes in.