Hot weather updates: Week of June 23, 2025

June 25, 2025 – 9:00 p.m.

ISO New England has lifted the precautionary Abnormal Conditions Alert. The system status has returned to normal.  

June 25, 2025 – 11 a.m. 

ISO New England continues to monitor grid conditions as hot, humid weather persists across the region. 

Consumer demand for grid electricity unofficially peaked Tuesday evening at 26,024 megawatts (MW), the highest level seen in the region since 2013. 

Following the unexpected loss of generation in the late afternoon, ISO New England managed the regional grid under a Power Caution. This step allows system operators to take additional actions, including calling on reserve resources, to balance the system. 

Weather conditions are expected to ease across the region throughout the day Wednesday, and consumer demand is expected to peak at approximately 24,000 MW. As of 8 a.m., ISO New England anticipated having a surplus of roughly 1,500 MW above the resources required to meet consumer demand and required operating reserves. 

A precautionary alert issued Monday due to the hot weather remains in effect. 

Significantly cooler weather is expected across the region on Thursday and Friday. 

June 24, 2025 – 9 p.m.

ISO New England has lifted the Power Caution as the evening peak has eased. A precautionary alert remains in place due to hot, humid weather across the region.

June 24, 2025 – 5:22 p.m.

ISO New England has issued a Power Caution for the region after the unexpected loss of generation left the region short of the resources needed to meet both consumer demand and required operating reserves. 

Declaring a Power Caution allows ISO system operators to take additional steps, including utilizing reserve resources, to balance electricity supply and demand. 

The ISO also declared an Energy Emergency Alert (EEA) Level 1, the lowest of three alert levels. 

A Power Caution is not an emergency, and the ISO is not requesting conservation. It is, however, a signal conditions on the system are tight and ISO system operators are taking additional actions to ensure power system reliability.  

Alerts like this are part of the ISO’s operating procedures and are available for operators to call upon when needed. 

June 24, 2025 – 1 p.m. 

ISO New England continues to monitor conditions on the regional power grid as hot, humid weather encompasses the region Tuesday afternoon. 

Consumer demand for electricity is expected to peak at approximately 25,800 MW between 6 and 7 p.m. If reached, this would represent the peak demand so far this summer but would be in line with ISO New England’s pre-summer forecast for above average weather. 

ISO New England expects to have the resources needed to meet consumer demand and required operating reserves, but system operators have tools that their disposal to balance the system if needed. 

June 23, 2025 – 9 p.m. 

ISO New England has issued a precautionary alert as hot, humid weather across the region could lead to tight operating conditions on Tuesday, June 24. This is not a system emergency. 

Known as an M/LCC2, this alert notifies power system operations, maintenance, construction, and test personnel, as well as other market participants, that they should suspend any testing or maintenance on their resources that could affect grid reliability. 

ISO New England continues to monitor system conditions and will provide further updates, as needed, in this space. 

June 23, 2025 – 1:30 p.m. 

ISO New England is monitoring system conditions as hot, humid weather drives higher consumer demand for electricity across the region. While the anticipated demand would be the highest seen this year, it would be in line with the ISO’s forecasts for the summer, and the ISO projects adequate supplies of electricity in the coming days.

Temperatures are expected to reach the upper 90s in Boston and Hartford, the region’s two largest centers of electric demand, on Tuesday, before tapering to more moderate temperatures later in the week.

As of Monday morning, ISO New England is forecasting the following peak electric loads:

• Monday, June 23: 23,920 MW
• Tuesday, June 24: 25,310 MW
• Wednesday, June 25: 23,130 MW

ISO New England’s system operators are well-trained to handle increased seasonal demand, unexpected generation loss, or transmission outages should they come to pass this week or any other day. System operators will continue monitoring conditions and have tools and procedures available to mitigate grid concerns if needed.

For more detailed information, visit the Seven-Day Capacity Forecast page.