The heat this week is doing something you can't see from your window. It's pushing the country's power grid toward a record. As a dangerous heat wave settled over the East and Midwest, the U.S. Department of Energy declared a grid emergency, with roughly 160 million people across 30 states under heat alerts. Energy Secretary Chris Wright called reliable power through the stretch "non-negotiable."

The number at the center of it: PJM, the nation's largest grid operator, forecast a record 166,304 megawatts of demand for Thursday, July 2, topping a mark that had stood since 2006.

And the nights bring no relief. Lows may struggle to fall below 80 degrees in New York, Philadelphia, Boston and Washington, so neither the grid nor the people leaning on it get a real break.

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The heat is hitting the grid from both sides

A heat wave squeezes the grid from both ends at once. It sends everyone's air conditioning into overdrive, and the heat itself makes power plants run less efficiently while power lines sag. Demand spikes at the exact moment supply gets shakier.

And the grid was already stretched thin, mostly by AI data centers and electric vehicles pulling record power before summer even started. That's why the federal response got unusual: to keep homes and hospitals on, the Energy Department cleared PJM to switch big data centers over to their own backup generators when the system runs tight. As one energy expert told Maryland Matters, the data centers are the reason "we're in a place where luck matters."

You can see the squeeze in the price. On Monday evening, the cost of wholesale power in PJM shot from under $40 to more than $1,600 in a matter of hours.

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Know your supplier: four cities, four situations

Your power comes from a local utility that runs on a bigger regional grid. Here's where the four biggest East Coast markets stand, and what each is asking of you.

New York: Con Edison (on the NYISO grid)

• How tight it is: demand is nearing New York's all-time record, and Central Park has officially hit its first 100-degree day since 2012.
• What Con Ed's doing: it turned on its emergency center and warned of scattered outages, and can dim voltage 5% across the system to keep the lights on.
• Your move: Mayor Zohran Mamdani's ask is simple: "Set your AC to 78 degrees."

Philadelphia & Washington: PECO and Pepco (on the PJM grid)

• How tight it is: this is the epicenter. PJM serves 67 million customers, and highs could flirt with all-time records near 106 degrees, with heat indices topping 110.
• Your move: PECO notes that about 40% of unwanted heat sneaks in through your windows, so close the blinds. Pepco says 78 degrees by day, 80 at night.

Boston: Eversource (on the ISO-New England grid)

• How tight it is: the calm one. Its peak is running below the record, so there's no conservation order.
• What Eversource's doing: it still switched on its demand-response program to trim the peak.
• The wild card: New England buys cheap power from Canada, which is in its own heat wave and may have less to share.

Will your power actually go out?

Probably not, but it depends. Grid operators run through a ladder of steps before anyone goes dark: conservation appeals, paying big users to cut back, shifting data centers to backup power and dimming voltage. Rolling blackouts are a last resort. Still, local outages from failed equipment or storms are always possible in heat like this, and as Monday's price spike showed, your bill can feel it even when your lights never flicker.

How to get ahead of it

Whether or not the grid holds, a few moves help.

• Ease the peak. Nudge the thermostat up (utilities across the region are landing on 78 degrees), close the blinds, and push laundry, the dishwasher and EV charging to late evening.
• Get outage-ready. Charge phones and battery packs now, keep water and flashlights handy, and have a plan for anyone on powered medical equipment.
• Stay safe. Extreme heat is one of the deadliest weather hazards there is. Find your nearest cooling center, and check on older neighbors and anyone without air conditioning.

This is the new normal

None of this is a one-summer problem. PJM's own planning now imagines demand as high as 169 gigawatts, and the forces driving it (data centers, EVs, retiring plants and hotter summers) aren't slowing down. The grid can be rebuilt for it. The question is whether that happens faster than the next heat wave arrives.

weather.com Content Development Manager Joy Kigin chases the stories where weather, science, and culture meet everyday life. She's a stickler for getting the facts right and a sucker for making them land, the kind of story that gets people talking (and, now and then, smiling).