Sorry to put such a fine point on this, but even without climate change, Phoenix, Arizona, is already pretty uninhabitable. Don't get me wrong, I spend a fair amount of time there, and I love it—particularly in the fall and winter—but without air-conditioning and refrigeration, it would be unlivable as is. Even with those modern conveniences, the hottest months take their toll on my feeble Southern Californian body and brain. The historical average number of days per year in Phoenix that hit 100 degrees is a mind-bending 92. But that number is rapidly rising as climate change bears down on America's fifth-largest city.

"It's currently the fastest warming big city in the US," meteorologist and former Arizonan Eric Holthaus told me in an email. A study from Climate Central last year projects that Phoenix's summer weather will be on average three to five degrees hotter by 2050. Meanwhile, that average number of 100-degree days will have skyrocketed by almost 40, to 132, according to another 2016 Climate Central study. (For reference, over a comparable period, New York City is expected to go from two to 15 100-degree days.)

And, tragically, all that heat costs quite a few Phoenicians their lives every year. Maricopa County keeps careful records of heat deaths and issues a morbid but extremely useful annual report. In 2016, 130 people died from heat—the most since the turn of the millennium and a big spike when compared to the 85 who died in 2015.

But as is the case with so much climate–related news, we shouldn't go rushing to blame climate change for these deaths directly. Yes, 2016 was a hot year—Phoenix's third-hottest ever, in fact—but, crucially, "it wasn't exceptionally warmer than many other years over the time period for which they've been gathering these statistics," Arizona State University climatologist David Hondula told me. (The exact cause of the spike in deaths remains a mystery.)

But Hondula told me that mystery just means that as the city heats up over the next few decades, there are other issues that deserve urgent public attention in the interest of saving people from getting cooked alive. These include"social service programs, homeless shelters, the opioid epidemic, [and] all these other intermediating factors," he said, adding, "If we're not paying attention to those at the same time we're keeping an eye on the thermometers, we might really miss some drivers and some threat magnifiers."

As bad as the deadly heat is getting, there's another potential horror coming: drought. "As much as 20 percent of the [Colorado] River could dry up by 2050," Holthaus told me.

The river is of enormous consequence to the fates of Arizonans. That's because an agreement they made in the 1960s says that among those drinking from the Colorado River (Southern Californians also guzzle from the same stream, for instance), Arizona would be the first state to ration.

But in 2012, the Department of the Interior put together a famous climate change study ("famous" among water researchers in Arizona, that is) showing a yawning chasm opening up between water supply and demand by 2060—a 3.2 million-acre-foot shortfall of water, to be precise. That's about five times as much water as Los Angeles uses in a year, according to the Washington Post.

Ray Quay, a researcher at the Decision Center for a Desert City project in the Global Institute of Sustainability at Arizona State University, told me, "Water is taken for granted right now." Soon enough, "a crisis will occur, and people will say, 'Oh my goodness, we have to do something. What do we do?' One of the problems we face is that nobody's really focused on that."

According to Quay, the first time the river level gets extremely low, the shortage will really only be felt by Arizona's farmers—meaning they'll start getting water from wells. "Going to groundwater and mining groundwater is not sustainable, because groundwater is not like some giant Lake Michigan under Arizona," he told me. "There will be impacts within that 2050 timeframe, but it's going to be spotty, and it's going to be in areas where the aquifers aren't as large. That's rural Arizona—particularly agriculture. You'll see some parts of rural Arizona where some people have to pick up and move."

"When the second shortage occurs, urban areas will feel that," Quay added.

"Agriculture and lawns will almost certainly be profoundly affected by then," Holthaus told me.

Quay told me that I shouldn't frame all these drought projections as climate change condemning Arizonans to all die of thirst. It's actually much more complicated than that. "All the rivers in the Southwest are highly volatile, and go up and down 20 percent from year to year," Quay explained, adding that that's "one of the reasons why the Southwest is probably one of the most prepared regions for short-term climate change in the country."

But solving these longer-term problems may turn out to be a tall order. As Quay pointed out, Arizona's water infrastructure was an invention of the mid-20th century—a time when the American government loved to spend money building stuff.

"The issues that we're going to be facing with climate change and drought, well, we're in an era when we don't have a lot of money anymore," Quay said.