Every Fall I do a post looking at historical Monsoon rainfall in Tucson, so let’s update it for 2020. Last year my concluding note was “Overall, it was a fairly unremarkable monsoon season, really nothing to write home about.” Well, that is certainly not the case this year. 2020, true to form, gave us plenty to write home about on the weather front as well! Just a few unpleasant milestones from this summer in Tucson:
- Second driest monsoon ever
- Hottest month on record first set in July then “bested” in August
- Hottest summer on record
- New record for 100-degree days in a year at a 100 through Sep 30, plus another 10 days in October that haven’t been officially confirmed yet
- Prior record for the full year was 99 days so 110 would blow that away
- If it makes you feel any better, Phoenix is at 145 days already
- August had 24 days of 105°+ heat, including 13 days in a row with highs over 105°
- Big Horn fire!
The weather service has blamed this summer’s unrelenting heat on a high pressure system that hung over the state and neighboring New Mexico much longer than usual.
Let’s look at some detailed monsoon stats. As mentioned above, 2020 was the second lowest rainfall for any monsoon season since 1895. Only 1924 had a lower total and even then by only 0.03 inches (Exhibit 1)! Let’s also review monthly rainfall in 2020 compared to Normal (Exhibit 2). We had zero rain in June, a little bit in July, decent amount in August and back to zero in September. Overall, this season was about 4.5 inches or 73% under the normal levels and even the best showing of 1.16 inches in August was still 50% below typical for that month.
Exhibit 1 – 10 Driest Tucson Monsoon Seasons in History
Exhibit 2 – 2020 Tucson Monsoon Compared to Normal
And lest you think that Tucson was the only dried out place, Exhibit 3 shows a comparison of 2020 season among major Desert Southwest metros. Every city was far below normal levels with Vegas and Yuma getting literally zero rain all summer.
Exhibit 3 – 2020 Monsoon by City
Here are a few links if you would like to play around with more detailed Tucson climate data: