New York's Grid Meets the Heat

On Thursday, July 2, 2026, the thermometer in Central Park reached 100 degrees. It was the first triple-digit reading in the park since 2012, tying a record for the date set in 1966, and with the humidity the heat index climbed to about 106, with a real feel closer to 110 or 115 in the streets. The reading was the peak of a heat wave the state grid operator called one of the most intense in more than a decade, a stretch of days when dangerous heat sat over the whole Northeast and every air conditioner in the region came on at once.

This is a briefing, written from inside the event rather than after it, and it uses the same live New York grid data behind Ask the Grid to answer a simple question: how did the electric system hold up. The short answer is that it held, but with less room to spare than the calm of a working air conditioner suggests. Demand climbed for six straight days to the highest level the New York grid had seen in years, the price of power in New York City spiked to nearly two thousand dollars a megawatt-hour, and the utility that serves the city cut voltage to hundreds of thousands of customers to keep the lights on. What follows is that week, in the numbers that recorded it.

Heat waves do not hit an electric grid all at once. They build. Each hot day warms the buildings, the pavement, and the people a little more than the last, and the overnight lows stop falling far enough to let anything cool off, so the load the grid has to serve steps higher every afternoon. That is exactly the shape the last week of June and the first days of July took on the New York system. System-wide demand peaked near 22,200 megawatts on June 28, then climbed to about 25,300, 26,200, and 29,600 over the next three days, and crested at 31,097 megawatts in the 6 p.m. hour on July 2 (nyiso.load_actual_hourly).

That 31,097-megawatt peak is the number to hold onto, because it sits in a meaningful place. The all-time record for New York State demand is 33,956 megawatts, set on July 19, 2013, during a similar multi-day heat wave. July 2, 2026 reached about 92 percent of that record, the closest the system had come to its ceiling in years, and it did so without the operator ordering anyone to cut back. Read the daily peaks in order and the climb is unmistakable: every single day of the heat wave topped the one before it, right up to the crest.

The most important thing the data shows about July 2 is not the size of the peak but the fact that it surprised no one. The New York Independent System Operator, which runs the state's bulk grid and its wholesale market, forecasts demand hours and days ahead so that enough generation is committed and ready. On July 2 that forecast was very nearly exact. Hour by hour, the day-of forecast tracked the actual load within roughly two percent all day, and it put the evening peak at 31,611 megawatts against the 31,097 the grid actually drew (nyiso.load_forecast, nyiso.load_actual_hourly). The peak was expected, planned for, and met.

This is what a well-run grid looks like under stress, and it is worth pausing on because it is the opposite of a market surprise. A forecast that lands on the peak means the generation was lined up in advance, the reserves were where they needed to be, and the operator spent the day managing a known quantity rather than reacting to a shock. It also meant the operator could see how thin the margin was getting, and it did what grids do when the cushion shrinks: it asked for help. With reliability margins tightening and some generation and transmission out of service, the operator issued public appeals for New Yorkers to conserve electricity where they safely could.

The conservation call went out across the state's leadership. Governor Kathy Hochul said her team had been coordinating with the utility, the grid operator, and city officials, and asked New Yorkers to set their air conditioners between 75 and 78 degrees and avoid running unnecessary appliances. Every degree higher on a thermostat and every dryer left off for the afternoon is load the grid does not have to serve at the peak, and in a week that reached 92 percent of the all-time record, that shaved margin is the difference between a tight day and an emergency.

Press play on the map below and scrub through the afternoon and evening of July 2. The whole control area is carrying heavy load at once, which is the signature of a weather event rather than a local one: the heat sat over the entire state, so every zone peaked together. Then follow the camera downstate, to where the load and the strain concentrate.

Forecasting the peak is one thing; holding the grid through it is another, and here the operator's own records show the effort in a way the load curve does not. Every grid keeps reserves, a cushion of generation held back so that if a large plant or a transmission line trips, the lost supply can be replaced in minutes. In quiet hours that cushion is nearly free. On the overnight of July 2 the price New York paid to hold ten minutes of reserve in the city was zero. Then the heat arrived, and the cost of the cushion climbed with the load.

By the middle of the afternoon it had gone vertical. In the New York City zone the ten-minute spinning reserve cleared as high as $1,066 per megawatt-hour and the thirty-minute operating reserve at $1,025, up from nothing overnight (nyiso.rt_ancillary_prices). When reserves price like energy, it is a direct read on how thin the margin has become: the grid is paying nearly as much to hold power back as to deliver it, because there is barely enough to go around. This is the same scarcity the energy price shows, seen from the reliability side.

To keep that cushion from vanishing, the operator worked down its emergency toolbox, and the dispatcher message feed logs each step. On July 1 it activated its Special Case Resources and its Emergency Demand Response Program, the paid, pre-registered demand response that pays large customers to cut load on command, the bulk-grid analog to Con Edison dimming a neighborhood. The day before the peak it requested emergency capacity from its neighbors, Hydro-Quebec to the north, New England to the east, and PJM to the west and south, for the July 2 afternoon and evening hours. Through the event it added emergency import transactions, executed reserve pick-ups when units tripped, cut hundreds of megawatts of locationally constrained load, and, on July 1 evening, ran the system in a formal thunderstorm alert state as the front moved through.

None of these is a blackout, and that is the point. They are the graduated, mostly invisible tools a grid operator spends before anyone loses power, and on these days NYISO spent a lot of them. The public saw a conservation appeal and a hot afternoon. The dispatcher's log shows demand response called, reserves priced like gold, neighbors leaned on for imports, and a thunderstorm alert running in the background, all so that the load curve on the previous chart could stay a smooth line instead of a cliff.

New York City is the hardest place on the system to serve. It sits at the end of the transmission network, hemmed in by how much power the lines into the city can carry, and its own in-city generation is limited, so when demand is high the city leans on expensive local units and on imports squeezing through constrained wires. That shows up as price. The wholesale price of electricity, the locational-based marginal price or LBMP, is the cost of the next megawatt at a given place, and in New York City on July 2 it told the story of a system reaching for its most expensive resources.

Through the small hours the New York City zone price sat near 60 dollars a megawatt-hour, an ordinary summer baseline. As the heat built it climbed, and then in the early afternoon it spiked hard: the five-minute real-time price for the city reached 1,847 dollars a megawatt-hour in a single interval at 1:35 p.m., roughly thirty times the overnight level (nyiso.rt_lmp_zone). It did not simply spike and vanish, either. For the rest of the afternoon and into the evening peak the city price stayed elevated, averaging between about 500 and 900 dollars a megawatt-hour hour after hour, a sustained premium that is what serving a heat wave at the edge of the grid actually costs.

The afternoon spike is worth one more look, because it separates this event from a routine hot day. The day-ahead market, which clears the afternoon before against a forecast, had priced the 1 p.m. hour in New York City at just 183 dollars. Real time delivered nearly ten times that. The day-ahead market did see the evening as expensive, clearing its highest price of the day, 808 dollars, for the 6 p.m. hour that lined up with the demand peak. But the sharp midday spike was a real-time event, the kind of thing that happens when a unit trips or a line binds on an already-stressed system, and the market that most participants watch the day before never priced it. The heat set the stage; the real-time grid wrote the ending.

The wholesale numbers above are the bulk grid, the high-voltage system the operator runs. But the place a heat wave is felt first is one layer down, in the local distribution network that Con Edison runs under the city's streets, and that is where July 2 and 3 got difficult. Heat degrades the underground cables and transformers that carry power the last mile to a building. To protect that equipment as demand surged, Con Edison reduced voltage by 8 percent across large parts of Brooklyn and Queens, a standard defensive move that dims the system slightly to relieve stress. At its peak the voltage reduction covered close to 400,000 customers, from Bay Ridge and Sunset Park to Forest Hills, Ridgewood, and Long Island City.

It was not enough everywhere. Between Thursday and early Friday more than 80,000 customers across the five boroughs lost power at some point, and in southwest Queens the utility took the unusual step of deliberately shutting off about 9,800 customers in Howard Beach, Ozone Park, Richmond Hill, and South Ozone Park so crews could repair heat-damaged equipment before it failed on its own. The company framed the shutoff as the lesser harm, a planned outage to head off a worse one.

This is the part of a heat wave the bulk-grid data cannot show you. On the wholesale system, July 2 was a well-forecast peak served without an emergency. On the distribution system underneath it, the same heat was cooking cables in Queens and forcing a utility to choose which neighborhoods to dim. Both things are true at once, and the gap between them is why a grid can look healthy in the aggregate while thousands of people sit in the dark. A related reminder of how tightly the region is stitched together came the same week, when a major transmission line that helps feed the city was briefly out, removing a chunk of import capacity at the worst possible time.

The response to the heat was not only technical. New York City activated its heat emergency plan, and Mayor Zohran Mamdani opened cooling centers across the five boroughs, listed through the city's cooling-center finder, while urging residents to help the grid directly. His ask was the same one the governor and the grid operator were making, translated for a resident with a window unit: turn the thermostat up a few degrees and switch off what you are not using, because on a day like this the margin is made of exactly those small choices.

Put the pieces together and the week reads as a system that worked hard and held. The bulk grid met a near-record peak it had forecast almost exactly, staying below the 33,956-megawatt record of 2013 and never requiring an operator-directed load reduction. The wholesale market did its job of pricing scarcity, sending New York City's cost to nearly 1,847 dollars a megawatt-hour to pull every available resource into service. The distribution utility spent voltage and, in one corner of Queens, a planned outage to protect its equipment from the heat. And the city and state leaned on the oldest tool there is, asking millions of people to use a little less at the same time. None of those alone would have been enough. Together they got New York through.

The heat did not so much fade as get shoved out. The cold front that finally displaced the hot air arrived the way summer fronts do, as a line of thunderstorms, and on the evening of July 3 it put on a show over the city: lightning over the harbor, a rainbow behind the Statue of Liberty, and then a sunset that turned the sky over Midtown a deep furnace red.

The storms drew people to the waterfronts with their phones out. One New Yorker caught the whole sequence from across the water, the lightning and then the furnace-red sky, the storm and the strange calm a heat wave collapses into, and posted it the next morning.

By the Fourth of July weekend the worst had passed. As the heat began to break, system demand eased back toward the mid-20,000-megawatt range and the New York City price settled to the mid-60s, the ordinary summer baseline it had started from (nyiso.load_actual_hourly). But the record from July 2013 still stands, and this heat wave came within 8 percent of it, in a city whose downstate load keeps growing and whose summers keep getting hotter. The margin held this time. Briefings like this one exist to measure it, day by day, so that the next time the heat builds for six days straight, the number that matters is already on the board.

Everything above is the same live NYISO data behind Ask the Grid. The figures come from nyiso.load_actual_hourly, nyiso.load_forecast, and nyiso.rt_lmp_zone, with the day-ahead prices in nyiso.da_lmp_zone. Open NYISO on the main map and scrub July 2, 2026 yourself.