U.S. power grids this week face a blistering heat wave across the East Coast and Midwest that is expected to break summer demand records, straining systems already pushed to the brink by surging energy consumption by data centers and electric vehicles.

PJM Interconnection, the largest regional grid serving 67 million customers, forecast record summer electric demand of 166.3 ‌gigawatts for Thursday evening, according to the grid operator's latest forecast. PJM's all-time summer demand ​record, set in 2006, is 165.6 GW.

PJM's planning for this summer includes what it has described as the "unlikely but plausible scenarios of up to 169 GW of demand."

The regional ⁠grid operator serves 67 million customers in the Mid-Atlantic, South, and Washington D.C. PJM says it ​has about 180.2 GW of generation capacity to serve demand, as well as 8 GW from programs that ⁠pay customers who voluntarily reduce their electricity use in times of system emergencies.

Temperatures are forecast to exceed 100°F (38°C) from Boston to Washington, D.C., near Northern Virginia's vast data center hub, driving a surge in air-conditioning demand that will further strain power grids ahead of ‌July 4 celebrations.

"When temperatures and humidity spike, increased demand for air conditioning can strain generation ​and transmission resources," warned ‌New York ISO, the grid operator for New York state. Peak demand in New York is expected to approach 32 GW on Thursday, just shy ‌of the record of nearly 34 GW, according to NYISO's forecast on Monday.

Meanwhile, electricity demand in MISO, the regional grid operator for 15 U.S. states in the Midwest and the South, is expected to ⁠challenge the peak demand record of 127.1 ‌GW, according to forecasts by the Midcontinent ⁠Independent System Operator (MISO).

To meet peak demand, MISO will rely on PJM, whose executives have been cautious about how the operator will handle ⁠what they call "a ⁠fundamental mismatch between how fast demand is growing and how quickly new supply can be built and connected to the grid."

"The region simultaneously faces ‌hyperscale data centers adding load at an unprecedented pace, accelerated policy- and economically-driven retirements of generation, and new power plants that now take roughly twice as long to build and cost twice as much as they did a decade ‌ago," PJM said ​in a May report.

What that means ‌is PJM is operating on a thin buffer against power plants tripping offline and persistent congestion on transmission lines.

On Monday evening, for example, the strain on PJM was evident as real-time ​electric wholesale prices surged to more than $1,600 per megawatt hour, compared with less than $40 per MWH earlier in the day. The evening price reflected heavy congestion on high-voltage lines during peak electric use.