How Much Hotter Will Your Hometown Get Over the Next Century?

Seattleites attempt to beat the heat at the Seattle Center's International Fountain. (Photo: Stephen Brashear/Getty Images)

Every August when I was growing up, my family stuffed an obscene amount of vacation gear into a wood-paneled station wagon and drove four hours across the Cascade Mountains from the Seattle area to Central Washington where it was hot. Legit hot.

It's not that Seattle and environs didn't experience summery temps during the few weeks a year not dominated by drizzle. Puget Sound summers were pleasantly warm-ish. But they were ultimately more on the mild side, which is why to this day Seattle is the least air-conditioned city in the United States. (Only one in three homes have central air or window units.)

Those multigenerational family vacations spent at a lakeside resort in Central Washington — dry, desert-y and hot Central Washington — were my very first experiences with temperatures above the 90 degree mark. Sometimes, they surpassed 100. Climatically speaking, it was a whole other world from where I came from — the Land of the Low 70s.

These days, my family has largely stopped making that annual summer pilgrimage across the Cascades. There are several reasons why. One of them, as my mom explained to me while I was visiting earlier this summer following a blistering Northwest heat wave, was because the blazing heat that was once such a novelty in Central Washington could now be experienced in western Washington with greater regularity. Why drive across the mountains through a wildfire-charred landscape when you could experience just-as-toasty weather at home?

"We went there every summer because part of the appeal was that it's so much hotter than home," she said. "Now it's just as hot here."

She had a point. And as she told me this, I couldn't help but notice how chilly I was standing in my childhood home — the same, AC-less house that my parents have lived in for over 40 years. After sweating through a brutal heave wave last summer, my parents — both mild weather-dwellers most of their lives — had done the unthinkable: they'd caved and installed central air.

The heat is on

Coney Island beach
New Yorkers hit the beach in Coney Island, Brooklyn, during an extended stretch of scorching weather in August 2018. The number of 'very hot' days per year in the Big Apple has steadily climbed since 1960. (Photo: Drew Angerer/Getty Images)

My hometown isn't the only city that's progressively gotten hotter over the past several decades.

An interactive graphic published by the New York Times in partnership with the Climate Impact Lab uses historical climate data and localized climate projections to chart the average number of days per year the temperature has reached 90 degrees Fahrenheit in your hometown.

Simply plug in your birth year and your hometown to compare how much hotter it is now and how much hotter it's expected to become by the end of the century or by the time you turn 80. (Oddly, Seattle doesn't pull up any results. According to the analysis, it is "not prone to 90 degrees days" even though this past summer the normally temperate city experienced at least 10 of them. So in my case, I'm left to rely on anecdotal evidence.)

When I enter my adopted hometown, New York City, I'm presented with a sobering, slightly sweat-inducing picture.

In 1980, the New York City area could expect an average of eight days per year when the temp reached 90 degrees or above. Today, New Yorkers can expect the thermostat to sail to 90 degrees or higher on 11 days per year on average. If I still happen to be living in the Big Apple when I'm 80 (god forbid), I can expect there to be 27 "very hot" days per year with the average range being between 16 and 34 days.

It's a similar, increasingly sweltering situation in another city I've lived in as an adult, Los Angeles. This time, I added 15 years to my actual age and plugged in my birth year as being 1965 (the dataset only reaches back to 1960). That year, L.A. residents could expect an estimated 56 days per year to reach 90 degrees or above. Today, that number has leapt to 67 days per year and is expected to jump to 82 days of 90-plus temps annually by the year 2045.

These projections are (optimistically) culled from data that assumes countries will be able to curb greenhouse gas emissions in line with their original Paris Agreement pledges. So in countries that fail to limit emissions, it's easy to imagine that the number of super-hot days will only be higher.

Humidity, health and the rise of 'heat days'

Hazy Jakarta skyline
Sunrise over Jakarta's smog-shrouded skyline in 2018. The Indonesian capital city is famous for sweltering climes ... and it's only getting hotter. (Photo: Bay Ismoyo/AFP/Getty Images)

According to the analysis presented by the Times, it's the already unholy-hot cities across the globe that will become exponentially more unbearable.

Jakarta, for example, experienced an average of 153 days per year with temperatures at 90 degrees or higher in 1960. Today, that number is 235 days per year on average. By the end of the century, nearly every day of the entire calendar year will be 90 degrees or hotter. Yikes. It's a similar situation in New Delhi, an oppressively polluted city that, once upon a time, experienced six months of 90 degree-plus heat annually. By the end of the century, that figure is expected to grow to eight months.

In Paris, a mostly mild but sometimes heat wave-prone city that's tackling climate change head-on under the leadership of Mayor Anne Hidalgo, it wasn't unusual for there to be a single 90-degree day in 1960. Now, three days of très chaud weather is the norm. By 2040, Paris will bake for an average of five days.

Kelley McCusker, a climate scientist with the Rhodium Group, tells the Times that humidity, which does not factor into the data, plays a significant role in how we're able to cope with gradually rising temperatures fueled by a changing climate.

"A very important factor for how humans experience heat is how humid it is," McCusker explains. "If it's also humid, humans can't physiologically evaporate sweat as easily, and we can't cool down our bodies effectively."

Children, the elderly, those who chronic medical conditions and low-income populations are the most vulnerable to the ill-effects of gradually rising temps.

Record-breaking temperatures in Phoenix, 2017
Residents of cities like Phoenix are already used to ultra-hot weather. Due to climate change, however, perilously hot days are due to become more frequent and intense. (Photo: Ralph Freso/Getty Images)

In a related article, the Times also reports on how "heat days" are on track to overtake snow days in frequency across the northeastern U.S. as an increasing number of school districts grapple with extreme heat impacting student performance — and health. In schools lacking air conditioning, early dismissals and cancelled after-school activities have become the norm well into September.

McCusker also notes that an uptick in super-hot days will be the most disruptive — and potentially deadly — in cities that aren't historically equipped to deal with frequent and prolonged stretches of such weather. Like Seattle, for example, or Montreal, another city where air conditioning is somewhat of a rarity. In cities like Phoenix, where residents are accustomed to existing within climate-controlled bubbles for long stretches of the year, periods of extreme heat will be longer and more intense. (In 1960, Phoenix experienced 154 very hot days; by the end of the century, that number is expected to jump to northwards of 180 days per year.)

Rapidly growing and economically booming, Dallas is one town that's aware of its increasing hotness. A sprawling city blanketed with concrete and hulking buildings, the urban heat island effect is profound here — no other American city with a population of over 1 million, aside from Phoenix, is heating up at a faster rate. Per historic data collected by the Climate Impact Lab, Dallas experienced 98 days of 90 degree or hotter weather in 1960. Although the number of super-hot days dipped in 1980, today Dallas residents can expect upwards of 106 super-hot days per year. By the end of the century, temperatures will top 90 for about three months of the year in Texas' third most populous city.

"More very hot days worldwide bring direct and dangerous impacts on people and the systems on which we depend," Cynthia Rosenzweig, head of the Climate Impacts Group at the NASA Goddard Institute for Space Studies, tells the Times. "Food, water, energy, transportation, and ecosystems will be affected both in cities and the country. High-temperature health effects will strike the most vulnerable."

After you've plugged in your hometown — or current city — into the Times interactive graphic, head over to the Climate Impact Lab to learn more about the methodology behind the estimates.