There’s a difference between climate and weather. Local meteorologist Nathan Tannenbaum describes it pretty neatly: “The weather is what we endure every day; the climate is what that weather turns into over decades in the same geographical area.” (He also recounts explaining climate to a second-grader, who defined it as “what you do with a ladder.”) Taken in those terms, summer 2017 wasn’t the worst we’ve seen in Las Vegas—but it did follow the decades-long trend of our Valley heating up.
According to figures provided by the National Oceanic & Atmospheric Administration-managed, Reno-based Western Regional Climate Center, Vegas’ mean average summer (June-August) temperature has been steadily increasing since 1949. With a mean temperature of 93.2 degrees Fahrenheit, 2017 was the warmest summer in nearly 70 years of recordkeeping. (2016 was the second-hottest at a mean of 93.1 degrees.) The WRCC’s Daniel McEvoy notes that Vegas’ overnight temperatures are increasing, too: “Again, 2016 and 2017 were [respectively] the second and first warmest on record.”
Weather-wise, the story is slightly different. In terms of daytime high temperatures, McEvoy says, “there is no clear upward trend.” But 2017 placed a strong third in mean maximum daytime temperatures, second to summer 2016. (Summer 1994 is first.) But again, that’s the stuff we endure daily. The difference between now and years past is that those hot days were offset by cooler nights, and days when the heat wasn’t quite so oppressive. That’s no longer happening.
So if this summer felt hotter, know that the figures back our suspicions—though we might be giving too much weight to extreme weather days. “There’s a psychological cycle,” Tannenbaum says. “When we get through a windy period, people tend to forget about it until the next one comes along, and then they say, ‘Damn, that’s windy.’” In other words, we can’t measure climate trends just by looking out the window.
Now, some good news: A hot summer doesn’t automatically mean we’ll see a cold winter. “It sounds like it might make sense, but that’s just not how it works,” Tannenbaum says. “Weather patterns are in constant motion all around the planet, and just because a certain set of weather patterns hangs out over one spot for however long they do, that doesn’t guarantee what’s upstream.”