Texas' power grid operator asked residents Tuesday to voluntarily cut back on electricity due to anticipated record demand on the system as a heat wave kept large swaths of the state and southern U.S. in triple-digit temperatures.

On the last day of spring, the sweltering heat felt more like the middle of summer across the South, where patience was growing thin over outages that have persisted since weekend storms and tornadoes caused widespread damage.

In the Mississippi capital, some residents said Tuesday that they had been without power and air conditioning for almost 100 hours, which is longer than the outages caused by Hurricane Katrina in 2005. Entergy Mississippi, the state’s largest electric utility, said its crews had worked 16-hour shifts since Friday, but some officials expressed doubts about its preparedness.

SOUTH FACING RAINY WEATHER, SCORCHING TEMPERATURES THIS WEEK

High temperatures in the state were expected to reach 90 degrees on Tuesday.

"The delay in restoring power has caused significant hardship for their customers and it is unacceptable," said Brent Bailey, a member on the Mississippi Public Service Commission, the state's energy regulator.

Texas heat

A Houston Astros fan operates a handheld electric fan at Minute Maid Park, the team's home field. The Electric Reliability Council of Texas has called on residents to slow their usage of air conditioning and other utilities as heatwaves lead demand to skyrocket. (AP Photo/David J. Phillip)

The request by the Electric Reliability Council of Texas, which serves most of that state's nearly 30 million residents, was its first of the year to cut energy consumption. ERCOT said it was "not experiencing emergency conditions," but it noted that the state set an unofficial June record on Monday for energy demand.

Much of Texas was under excessive heat warnings Tuesday that were set to stay in place until Wednesday, with forecasted heat indexes surpassing 110 degrees, according to the National Weather Service.

RECORD-BREAKING HEAT SCORCHES SOUTH; PARTS OF TEXAS COULD TOP 120 DEGREES

Many Texans have been skeptical of the state's grid since a deadly 2021 ice storm knocked out power to millions of customers for days. Republican Gov. Greg Abbott has said improvements since then have made the grid more stable, but those improvement efforts continue to draw scrutiny.

In neighboring Oklahoma, more than 100,000 customers were eagerly awaiting the restoration of power and air conditioning following weekend storms that downed trees and snapped hundreds of utility poles. Officials say at least one person in Oklahoma has died because of the prolonged outages, which could last into the weekend for some residents.

Arkansas Gov. Sarah Huckabee Sanders on Tuesday declared a state of emergency because of the weekend’s storms, citing damage from the weather and "numerous" downed power lines.

CLICK HERE TO GET THE FOX NEWS APP

In Louisiana, the Southwestern Electric Power Company said more than 93,000 of its customers remained without power Tuesday morning. Nearly half them were around Shreveport, where the utility has estimated power would be restored by Saturday night.