Someday in the not-too-distant future, the effective temperatures in New York City will hit 120 degrees. If you were in the five boroughs during the three-day mid-July heat wave where it felt like 110 degrees Fahrenheit, according to the National Weather Service , you got a taste of what extreme heat can do to a city. 50,000 people lost power , the New York Triathlon and other events were canceled , and officials advised people to head to " cooling centers " like libraries and senior centers where they could avoid the heat.

But when NYC's heat index —a measure of how hot it actually feels to humans—hits 120 degrees, the consequences will be even worse. Here are some possible scenarios, as outlined by experts VICE spoke to:

"Urban areas are warmer in the same time period than their rural counterparts," said Spaccio. "And that’s basically due to the infrastructure of the city, and how they're built."

To understand the problem, it’s first worth understanding just why New York City is so hot in the first place. A phenomenon known as the urban heat island effect is the culprit, said Jessica Spaccio, a climatologist at the Northeast Regional Climate Center at Cornell University.

Extreme heat is often called a "silent killer": Unlike hurricanes, tornadoes, and droughts, it’s hard to visualize a heat wave on TV or in photos. There are no flooded homes or ripped-up buildings. But thanks to climate change "extreme heat events" are likely to become more and more common, putting strain on cities like New York and placing their citizens at risk.

"It's not like we're projecting what could happen based on science. I mean, these are things that have happened," said Kurt Shickman, the executive director of Global Cool Cities Alliances , which advises urban centers worldwide on mitigating this phenomenon. "We're really saying these are things that happen when it gets hot, and not even that hot. And if it all happened at once, it can essentially shut a city down."

None of that is particularly far-fetched. A January heat wave in Australia melted a highway , hot air grounded planes in Phoenix in 2017, the sun warping railroad tracks is a well-documented phenomenon, and high temperatures caused at least six deaths in the U.S. during that July heat wave.

Tall buildings impede airflow, and the city is short on green spaces that might cool the air by reflecting heat, consuming hot air to turn into oxygen, transpiring water into the atmosphere, and providing shade. Cue an egg frying on the sidewalk.

Asphalt and concrete make up 28 percent of New York’s surface area . These surfaces tend to absorb heat, rather than reflect it back into the atmosphere; as a result, the surrounding air stays hotter for longer—which is why nights are often just as sweaty as the daytime during heat waves. "There's no overnight reprieve," Spaccio explained. "You can't just open the window and let cool air in. You have to keep everything shut, and keep the A.C. going constantly."

One important consideration, Shickman said, is that temperatures vary wildly throughout the city. The official measurements are taken in Central Park—a leafy, green area likely to be relatively cool. "When we talk about the average temperature in New York being 120,” Shickman argued, “well, the reality is that it's 120 in the stations that they take temperatures, but in the South Bronx, I'll bet it'd be 125, 130.”

By 2050, baseline temperatures in New York are estimated to increase between 4.1 and 5.7 degrees, with double the number of summer days above 90 degrees. Spaccio said that a heat index of 120 would require a temperature of 96, with a relative humidity of 65 to 70. "If we see our baseline temperature warm as the globe is warming, then it's easier when we have hot days to get above that," she said.

The New York City heat wave in July set a weekend demand record: 12,063 megawatts. (The city normally uses about 11,000 a day.) Con Edison, the city’s primary power supplier, said this usage is what left thousands of customers without power. Worse still, these outages affected a number of low-income communities of color considered to be at high risk for heat deaths.

"That's a substantial number, and it's going to be likely above what the capacity of the grid can deliver for that kind of power," he said. "So that's going to be a significant challenge."

One major cause of concern as temperatures rise, Shickman said, is the electrical grid. Shickman's organization found that in Washington, D.C., when maximum temperatures reached 95 degrees residents were demanding up to 40 percent more power from the grid, due to cranked-up air conditioners. Now imagine even higher temperatures pushing that even further.

So what can cities like New York do to survive the sweltering heat? Shickman pointed to a number of short- and long-term strategies, many of which are being deployed worldwide. More roofs could be painted white in order to reflect heat. More green space would also help. Underground areas should be ventilated. And cooling centers should be widely accessible. This summer, Paris—where 500 people died in 2003—launched its new emergency heat plan, which kept public fountains, misting stations, and parks running late or all hours. (By 2050, the city hopes to have its 800 schools turned into cool spaces.)