This summer is on track to be the hottest on record in New York City. New Yorkers have already faced three heat waves by the end of July, with late summer heat looming around the corner.

There’s perhaps no better place to feel temperatures rise than stepping onto a subway platform. In past years, RPA has found that some station platforms reach a temperature of 100 degrees, with many others hovering in the mid-to-high 90s.

This year, RPA took a more abbreviated approach to measuring heat in the subways, with similar results:

Previously, RPA has described what makes the subways hot — braking and accelerating generates heat, running air conditioning on the cars pumps hot air into the system, subway cars sitting in the station increase temps, and so on. Some stations also house signaling technology — the communications equipment generates heat in the system as well.

These operations are just a fraction of why it gets so hot. Simply put — if it’s hotter outside, it’s hotter down below. Climate change is driving higher average temperatures across the globe; it’s not hard to imagine the platforms getting hotter and more uncomfortable as New York experiences more summer heat.

Cars especially drive temperatures in urban environments. It’s well known that greenhouse gas emissions from transportation are a major driver of climate change. But more granularly, car engines generate and radiate heat. If hundreds or thousands of cars are running in one place, it’s going to get hot. Add to this the urban heat island effect — concrete buildings and sidewalks absorbing heat, little shade, and so on — and the city and its subway stations are going to feel even hotter.

All of this, coupled with a lack of airflow and very little system-wide cooling systems, means that New Yorkers are bound to have a hot trip.

There are a few ways to look at addressing the problem: the infrastructure of the system, the operations, and the bigger picture.

Upgrade infrastructure

The New York City subway system is over 100 years old. The first modern AC systems were only developed a few years prior to the New York City subway starting its operations in 1904. Simply put, a good amount of the stations across New York were not built to have air conditioning. Adding fans to the platforms to move air around is feasible, but actually dropping the ambient temperature with air conditioning or chilling may not be physically possible due to the physical constraints of the stations.

Still, the MTA is looking into ways to cool down the platforms, as noted in the Climate Resilience Roadmap from April of this year. More recent stations already see these benefits. 34th Street-Hudson Yards, which opened in 2015, has an air conditioning system that keeps the platform between 72 and 78 degrees. Other stations, like the Grand Central-42 Street stop, have air chillers overhead that keep heat in check. In the case of Grand Central, it’s happenstance — the chillers that keep the platform cool are what keep the terminal above air conditioned.

Increase system service

Improving the efficiency and frequency of subway service could also help. Decreasing the amount of dwell time — meaning, decreasing the amount of time that a train waits at the station — would mean heat gets pumped into the tunnels as the train moves, not the platforms as it sits still.

Less stopping and starting would also help with this. Better subway service means modernizing the signaling systems, getting better rolling stock, and repairing breakdowns as quickly and efficiently as possible.

Address the bigger picture

While infrastructure and service improvements could help address heat on the platform, there is also the underlying issue of climate change and extreme heat. As greenhouse gas emissions continue to increase, so too do global temperatures.

Compounding that is the urban heat island effect. Research in recent years shows that the concentration and retention of heat from built environments doesn’t just affect surface temperatures, but sub-surface temperatures as well.

Again, the subway was built before AC was widely adopted — but it was also built for a climate that simply does not exist anymore. Global temperatures have risen 2 degrees Fahrenheit since the 1850s, and the rate of warming has gotten faster since the 1980s. The rate of heatwaves in U.S. cities have doubled since the 1960s.

To make a long-term difference on the way we experience heat in the subways, we need ambitious commitment to climate action. Within the transportation sector, that means reducing dependency on cars, reducing vehicle miles traveled (VMTs), incentivizing mass transit, and so on. It also means a just transition away from fossil fuels.

Without meaningful climate action, infrastructure improvements are null and void.

Until Governor Kathy Hochul’s unexpected reversal at the beginning of June, New York City was to be the first city in the nation to enforce congestion pricing, which would have simultaneously decreased the amount of cars on the roads (and thus transportation emissions) while increasing funding for the MTA capital program, which pays for upgrades to the transit system.s. With the indefinite pause on congestion pricing, there’s no plan to reduce traffic or replace the $16.5 billion dollars congestion pricing would generate.

Of the infrastructure and service improvements outlined above, few can be achieved without New York’s congestion pricing law. As discussed in recent MTA board meetings, the current capital plan is now restricted to maintenance and state of good repair work; bigger, more innovative projects, like adding air chillers and rethinking how we cool an open system, will be shelved for the foreseeable future. The board reiterated that in its July 2024 board meeting — the agency could be in a deficit as soon as 2026. Signal maintenance, which improves how efficiently trains move through the system, is already deferred on a number of different lines throughout the boroughs. That means stopping, starting, and dwelling are all inevitable, if not doomed to get worse. And this fall, the MTA will announce its draft 2025-2029 capital program, which will require tens of billions in new funding.

Additionally without congestion pricing there will be little to deter driving in New York City. One could argue that a subway system doomed to disrepair — and to uncomfortable temperatures — may even incentivize private car use, which would run counter to climate goals. We know that traffic is already worse in New York than it has been ever before. Even with infrastructure improvements and more frequent service , the problem will only get worse with rising temperatures.