(NewsNation) — Large parts of the country could see rolling power blackouts on some of the hottest days of the summer this year.

Extreme weather, according to Reuters, is causing increasing challenges for power grids across the United States. Officials are concerned that the record heat and drought the country has seen could mean rotating blackouts in several regions.

A May report from the North American Electric Reliability Corporation said a combination of drought, heat, potential cyberattacks, geopolitical conflicts and supply chain problems could disrupt the power supply.

NERC’s report said the Midwest is at especially high risk because of the retirement of older energy plants, causing decreased capacity from last summer and increased demand.

Planned maintenance and forced outages are threatening the Midwest’s summer generating capacity, too, as well as the shutdown of coal and nuclear plants.

The Midcontinent Independent System Operator, which is the region’s grid operator, has already warned of potential capacity shortfalls and other reliability concerns in the north and central regions of its coverage area.

Plummeting river levels could also cripple hydropower production in the Southwest, NERC warned. Texas’ drought-related heat events could cause an extreme demand for energy.

The Washington Post reports that New Mexico’s attorney general is preparing for worst-case scenarios, along with North Dakota and Arkansas officials.

In California, officials are warning residents that more than 1 million addresses could go dark this summer.

“Industry prepares its equipment and operators for challenging summer conditions. Persistent, extreme drought and its accompanying weather patterns, however, are out-of-the-ordinary and tend to create extra stresses on electricity supply and demand,” said Mark Olson, NERC’s manager of reliability assessments. “Grid operators in affected areas will need all available tools to keep the system in balance this summer.”

MISO said it and member utilities have trained for worst-case scenarios this summer, and are prepared to take action to maintain grid reliability. This includes urging homes and businesses to conserve energy and limiting power plant and transmission line maintenance during heatwaves, along with the rotating blackouts.

Reuters and Nexstar Media Wire contributed to this report.