By John Simpson
May 2019 was very cool for southeast Arizona and depending on what part of area you live in, it was either very wet, or just average. Let’s start with temperatures first.
The Tucson Airport recorded the 23rd coolest May since the 1880’s and the coolest May since the 1970’s. The average overall temperature for May 2019 was 5.1 degrees below average, the largest departure from average the airport has recorded for May since the 1950’s. If we focus on the last half of the month, the average high temperature from the 16th to the 31st was 83.5 degrees, which is well below the 30-year average of 94.2 degrees. Of course, Vail is somewhat cooler than the airport.
May 2019 was very pleasant and for those of you participating in or watching outdoor sporting events such as track or baseball, you were probably wondering if it really was May. Persistent upper level trofiness in the western U.S. (as the National Weather Service states) was the reason for the cool weather. This also brought above average rainfall to much of the west, although for southern Arizona it was hit and miss. Much of the rain occurred on the 11th and 12th. My place in Central del Lago only received 0.08” of rain for May, which is about my 8-year average of 0.06.” The airport on the other hand was right under an isolated storm on the 12th and received 1.11” that day, making it the second wettest day in May in its history. The airport recorded 1.22” total for May 2019, which is well above its 30-year average of 0.23” and the second wettest May since the 1880’s.
Some parts of Vail received decent May rain such as Kolb and I-10, which received about 0.8” and parts of Rita Ranch, about 0.5.” Much of the eastern half of Vail only received a quarter inch or less. For the spring season (March-May), the airport received 1.91” which is above its 30-year average of 1.27” and the first time the airport has recorded normal or above normal spring rainfall since 2004. I recorded 0.96” (half of what the airport received) which is above my 8-year average of 0.78.” Remember, spring 2018 essentially no rain fell. To see the amount of rain you may have received in your area, go to rainlog.org. Other notable rainfall amounts for reporting stations in the west for May 2019 compared to normal are listed in the following table.
Location Normal May Rainfall May 2019 Rainfall
Salt Lake City, UT 1.95” 3.78”
Las Vegas, NV 0.12” 0.80”
Kingman, AZ 0.13” 0.85”
Flagstaff, AZ 0.63” 3.02”
Phoenix, AZ 0.11” 0.10”
San Diego, CA 0.12” 0.80”
Los Angeles, CA 0.22” 0.73”
At the time of this writing in early June, the Tucson Airport has yet to reach 100 degrees for 2019 and the days remain slightly below average temperature wise. What about the upcoming monsoon season? The continuing presence of El Nino and other factors such as high snowpack in the West and high soil moisture content to our East are leading to greater than average chances for a late start to the monsoon and possibly below average rainfall, at least early in the season.
An above average number of tropical systems in the eastern Pacific is forecasted, which could lead to increased moisture for southern Arizona later in the monsoon season. To see the official monsoon outlook and the May climate report for the area, go to the Tucson National Weather Service’s website or Facebook page. For next month’s article I will report on June and give an update on the 2019 monsoon season.