Q&AZ: Why is Arizona so hot?

It’s no secret that Arizona is hot.

But via KJZZ’s Q&AZ reporting project, one listener asked a simple question with a less simple answer: Why is it so hot?

And the answer isn't quite as simple as “because we live in a desert.”

According to Kaitlyn Trudeau from Climate Central, Arizona’s climate - like every other place on Earth - is shaped by six key factors: ”There’s latitude, altitude or elevation, atmospheric circulation, how close you live to large bodies of water, ocean currents and topography,” she said.

In terms of latitude, most of Arizona sits in a valley around 30 degrees north of the equator, which is where Trudeau says most of the world’s large deserts are found.

The Sonoran Desert, part of which makes up a significant portion of Arizona, ranges from 25 to 33 degrees north of the equator - and the Sahara Desert ranges from 23 to 25 degrees north.

Of course, there’s also no oceanfront property in Arizona, since it’s landlocked by Mexico, California and several other states to the north and east.

And the Sonoran Desert is surrounded by mountains that Trudeau says cast a “rain shadow” over the Valley, limiting the precipitation the desert sees.

When moist air blows up against the mountains from one side, the moisture gets sapped out of the air as it goes over the mountains, leaving only dry air, giving us our signature phrase: “But it’s a dry heat!”

Another thing Trudeau says is affecting Arizona’s climate? The ever-increasing population.

”As the population grows, you see a stronger increase in that urban heat island effect,” she said, “because a lot of the materials we use absorb more heat.”

The urban heat island effect is partially responsible for increasing nighttime temperatures in the Phoenix metro area, Trudeau said.

During the day, when it’s hot and sunny, the vast amounts of concrete and asphalt in the metro area’s cities absorb the sun’s heat. And after the sun goes down, all that heat re-radiates back into the air, driving nighttime temperatures up.

“And so it’s not just the days. It’s not just the maximum temperatures getting high - it’s also the minimum temperatures getting really high,” Trudeau said, “Which has all kinds of implications for human health, activities, vegetation, ecology, all those kinds of things.”

Climate change is also making Arizona hotter, according to Trudeau.

”We’re able to look back millions and millions of years and see what the temperature was like,” she said. “We know that the rate of warming we’ve seen in the last 50 years has been faster than anything we’ve seen in at least the last 2,200 years.”

Trudeau said she’s optimistic about the future though, based on the past:

”We had a huge hole in the ozone, and countries actually came together and took action and we’ve seen the ozone bounce back,” she said.

So, the answer to “why is it hot?” is quite a bit more complicated than “because we live in a desert.”

But if you want to keep it simple, that’s not an inaccurate statement.