t should come as no surprise to hear Tucson endured an exceptionally hot and dry summer this year. Many folks stuck at home due to the enduring pandemic had little to do but wait for the relief the monsoon often brings, but 2020 appears set on stacking up the hardships.
The monsoon generally drops just over 6 inches of rain from June 15 through September, according to the National Weather Service. So far, monsoon 2020 has resulted in only 1.6 inches, as measured at the Tucson International Airport.
While Tucson’s rainiest months are often July and August, NWS maps the monsoon through September. However, little rain is forecast for the coming weeks, meaning monsoon 2020 has the potential to land among the top 10 driest monsoons recorded since 1895.
All the more bitter is how promising this year’s monsoon kicked off. On Saturday, July 11, a massive storm rolled in from the east with gusts topping 60 mph, felling multiple trees and drenching parts of the Tucson valley. But no storms in the following months matched this initial power.
“We’ve got a fairly good chance of ending in the 10 driest on record, I’m guessing about a 75 percent chance,” said John Glueck, senior forecaster for the National Weather Service in Tucson. “The moisture mostly kept to our south. It was never in a good position, like in the Four Corners area, for a good period of time. It was suppressed, which kept the bulk of the moisture south of the border… For the most part, Tucson is on the edge of the monsoon, and we need a certain kind of wind pattern to get us in a position to see the storms.”
On a monthly breakdown, June generally sees .15 inches, July sees 2.25 inches, August sees 2.39 inches, and September sees 1.29 inches. For 2020, June had no rain, July had .46 inches, August had 1.16 inches, and the rest of September remains to be seen, though little rain is forecast.
Luckily, this weak summer rain is not a trend for recent years. While monsoon 2019 also saw below average rainfall, 2015 through 2018 all saw above average monsoonal rains, with 2017 seeing nearly 50 percent more rain than average.
“If you look seasonally, there aren’t many trends in the full monsoon, but if you look on a month-by-month basis, the Augusts have been pretty dry for the last 15 years. For the most part, they’ve been well-below normal,” Glueck said.
However, rainfall is only one part of the equation. August 2020 was also Tucson’s hottest month ever recorded since 1895, beating the previous record set by … July 2020. Both months combined to make this summer the hottest in all 125 years of weather records. According to NWS data, this August held a combined average temperature of 92 degrees. This July held a combined average of 91.5. Before these last two months, the hottest month was July 2005 at nearly a full degree lower.
The average August temperature over the last 125 years is 84.7 degrees, and the average July temperature for the same range is 86.5. These temperatures are not daily highs, but averages over the entire month—highs and lows. And while these last two were the hottest months on average, the maximum temperature recorded in Tucson was in June 1990 at 117 degrees.
“The trend is for warmer, and we’ve had hotter summers for a good period of time now, and that’s something we’ll just have to get used to with a warming climate,” Glueck said. “But with it being warmer, there should be the potential for more moisture and more localized heavier rain events than we had in the past, so the extremes may increase with time.”
Looking forward, the upcoming winter is headed into a moderate La Niña, sometimes referred to as the “cold phase” of the El Niño-Southern Oscillation cycle.
“The forecast for this winter will most likely be for drier than normal conditions,” Glueck said. “We’ll still see some storms coming through, but there should be less of them. This is not a good combination, coming out of a hot and dry summer, going into a dry winter. Our drought conditions will deteriorate even further.”
Coming off this particularly brutal monsoon, Tucson’s Mayor and city council declared a climate emergency at their September 9 meeting.
“With record-breaking temperatures, increasingly dry summers, and historic wildfires, the need to act boldly to combat climate change and build resiliency in our city has never been more apparent,” Mayor Regina Romero said during the declaration. “By establishing bold goals, and expanding on our current efforts, the City of Tucson is well-positioned to act as a climate leader and become a more ecologically, socially, and economically sustainable city.”
The declaration sets a goal of the city reaching “carbon neutrality”—or achieving net zero carbon emissions, either through eliminating emissions or carbon removal—by 2030. The 10-year Climate Action and Adaptation Plan prioritizes the city to transition away from fossil fuels, using renewable and locally sourced energy, massive tree-planting initiatives, conservation of water, and building more sustainable infrastructure. In this plan, Tucson is joining more than 1,700 cities and jurisdictions across the world that have committed to reducing their emissions.
“Hopefully this was the worst monsoon we’ll see in our lifetime,” Glueck said. “I think statistically we will see better monsoons.”