"The ice broke on the Santa Cruz River today."
That's what we hear on the first 100-degree day each year. Maybe it makes us feel better about heading into that long stretch of hot summer days if we pretend there was ever ice in that mostly-now-dry river.
Has there ever been a summer in Tucson without a single 100-degree day?
That fantasy hasn't happened since we started recording Tucson temperatures in 1895.
We hear all the time about the first 100-degree day each year. The earliest it has happened is April 19; that was in 1989. The latest date we reached 100 degrees for the first time was June 22 in 1905. The average first 100-degree date is May 25; the normal first 100-degree day is May 18. Average is for the period 1894-2021. Normal is for the period of 1991-2020.
But what about the last 100-degree day each year? That day isn't heralded with trumpets because, of course, we don't know for sure that it won't happen again each year. But it must be a date many of us would look forward to if we knew when it was coming.
The average occurrence of the last 100-degree day in Tucson is Sept. 18, and the modern normal is Sept. 24. The earliest final 100-degree day was in 1966 on Aug. 8. The latest was 1991 on Oct. 16, when we had a record high of 100 degrees. We both tied and broke that record in 2020. We tied the record for the latest day of 100 degrees or more and set a new record high of 101.
We thought it bad in 1994 when we had 99 days in which the temperature reached at least 100 degrees — only 82 of them actually in the summer months. In 2020, however, we learned we can now look back on 1994 fondly. We had 108 days of 100 degrees or more, about 60 percent of them in the summer months.
We probably all know that the record high in Tucson was 117 degrees on June 26, 1990. Do we know the record low? Do we care? For those who do, it was six degrees on Jan. 7, 1913.
The Star archivist went in search of articles about the first 100-degree day each year and couldn't find them in the Arizona Daily Star in the earliest years of record keeping. She surmises that before air conditioning, perhaps Tucsonans didn't want to know just how hot it was when there was no escape for those who had to remain in Tucson to attend their jobs.
There comes a point when we must accept the heat, which is far easier to do when we have air-conditioned homes to which we may retreat.
The date at the beginning of each story here is the date the story ran online or in the paper. Of course, before the Internet, these stories ran the day after the mercury hit 100.