In the hot seat
The snow giveth, the heat taketh away

In the hot seat

A retardant drop on the York Fire in the Mojave Desert./ Courtesy of National Park Service

Jonathan Thompson - 08/03/2023

Now that July is over, the official meteorological diagnosis of the month is in: It was friggin’ hot! On a global level, it was the hottest month on record, maybe even the hottest in the last 120,000 years. The figures for the West aren’t in yet, but I think we can all agree it was an abnormally warm and dry month for most places.

Phoenix experienced a full month – i.e. 31 consecutive days – of 110+ degrees Fahrenheit (from June 30-July 30; the streak was broken July 31, when the mercury topped out at a chilly 108 F). That included three 119-degree days and a record-breaking overnight low of 97. And the average daily temperature for the month was nearly 103 degrees, shattering the old record and more than seven degrees above “normal.”

Although the monsoon has made it to some parts of southern Arizona, dumping three-fourths of an inch of rain on Tucson and knocking out power to some 50,000 people, it’s missing other parts of the state. Phoenix-proper hasn’t received measurable precipitation since March 22. Ugh.

Sure, that’s Phoenix, which is always a cauldron. But how about these all-time record-breakers?:

• 120 F: Maximum temperature in Ajo, Ariz., on July 20, breaking the previous record of 119 F set in 2021.

• 93 F: Maximum temperature in Del Norte – at nearly 7,900 feet above sea level – on July 26 and 27, breaking the record set in 2015.

• 85 F: Maximum temperature at Parker Peak, Wyo. – 9,400 feet in elevation – on July 24, breaking the record set a day earlier (previous record: 82 F set in 2002).

• 78 F: Minimum temperature at Bredette, Mont. – in the northeast corner of the state near the Canadian border – on July 23.

The point being: it’s hot everywhere, even in the high country, and even in the coolest part of the night in Montana.

The good news is that all that heat was preceded by a really wet winter and spring, saving us from complete disaster. The bad news is the heat has conspired with a late-arriving monsoon to suck up a lot of that moisture, leaving less for the rivers and vegetation.

The big winter resulted in a big spring runoff, naturally. But the high heat + low spring-summer precipitation melted and evaporated the snow, dashing hopes of an extra-long rafting season on many streams. After running far above median levels even into late July, many rivers – including the Dolores and Animas – are now running below normal for this time of year. That ripples downstream to Lake Powell, where inflows have also dropped rapidly since July 1 and are now even below 2022 levels for this date, causing reservoir levels to drop 4 feet in less than a month. A good, Colorado Plateau monsoon will help fix that – if it materializes – but continued heat will continue to sap moisture from streams and reservoirs.

This all meshes with a new study on climate change’s effects on the Colorado River. The researchers nicely summarize the key points of the study:

We find that the basin has roughly 10% less water available under present-day conditions due to warming since the 1880s. The majority of water loss has occurred due to a heightened sensitivity to warming in the basin’s regions associated with snowpack, compared to regions without snowpack. We also demonstrate that without this warming, the Colorado Basin would have had significantly larger amounts of water available, equal to the size of Lake Mead, over the duration of the 2000–21 megadrought.

Did you get that? Climate change has stolen a whole Lake Mead from the Colorado River over the past couple decades, and the hydro-thievery will continue and even accelerate as temperatures rise.

This should provide yet more impetus to stop burning fossil fuels in the hope of slowing warming. But it also should be a reminder that even if drought subsides, the big aridification has not ended. We can’t be lulled into complacency by a good snow year, even a record-breaking one, or some flash-flood-triggering downpours. Lake Powell is still less than 40% full. The Colorado River still carries less water than has been allocated to its users, meaning they collectively must cut consumption by at least 2 million acre-feet per year, likely a lot more. Easing water-use restrictions is a bad idea. The heat is in it for the long haul, I’m afraid, and we must act accordingly.

Land Desk is a newsletter from Jonathan P. Thompson, author of “River of Lost Souls,” “Behind the Slickrock Curtain” and “Sagebrush Empire.” Subscribe at: