Story highlights More than 160,000 customers are out of power Sunday night

The Virginia governor asks residents for their patience

While temperatures cool in the East, forecasters see the Southwest heating up

The cold front will continue moving south through Tuesday

The relief was short lived.

A cold front that pushed through the Midwest and Northeast on Sunday, finally breaking a stubborn heat wave, brought with it fresh storms -- complicating recovery efforts in some places and causing even more damage.

"It has been a tough few weeks for many Virginians. They have suffered from record breaking temperatures and an historic storm that brought widespread damage and power outages. Now, many have lost power again. I ask Virginians to remain patient and to continue to help each other get through this latest storm," Virginia Gov. Bob McDonnell said late Sunday.

Including Virginia, more than 160,000 customers in nine states and the District of Columbia remained without power. Some have lacked electricity for more than a week.

The hardest-hit state continues to be West Virginia, where almost 70,000 customers had no power Sunday night. Because utility companies typically define each residential and business account as a customer, the actual number of people affected was higher.

The heat wave that roasted much of the country for more than a week left scores dead and millions without power at one point -- many of them following a round of severe storms that swept the Mid-Atlantic states on June 29.

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And more hot weather may be on the horizon.

The National Weather Service has issued excessive heat warnings for parts of Arizona and California starting Monday, predicting temperatures in the range of 110-115 degrees.

"The combination of hot afternoon temperatures and very warm overnight lows will result in oppressive conditions," the weather service said.

Early Sunday, heat advisories, watches and warnings were posted for portions of 11 states -- less than half the number of states that have seen them the last few days, said CNN meteorologist Sarah Dillingham.

The cold front will reduce temperatures into the 80s for Chicago, New York and Washington, and into the 90s for St. Louis by Monday, she said. It will continue moving south through Monday and Tuesday, CNN meteorologist Alexandra Steele said.

One person died and a second was injured in the east-central Missouri town of Cuba on Saturday in storms, according to the weather service's Storm Prediction Center. Damage including building collapses, vehicle rollovers and downed power lines were reported, the center said. Another injury was reported Saturday in Mifflinburg, Pennsyvlania, officials said.

Nationwide, there have been more than 4,500 daily record highs in the last 30 days, according to the National Climatic Data Center.

Temperatures topped 100 degrees Saturday in a swath stretching from south-central Iowa to the Chicago area to Louisville, Kentucky, to Virginia, the weather service said. A high of 105 in Washington on Saturday marked the second-hottest day on record for the city and the 10th straight day of temperatures above 95.

Saturday's death in Cuba, Missouri, came as debris struck a woman's car in a grocery store parking lot during a severe storm, CNN affiliate KMOV reported.

A 4-month-old girl in Greenfield, Indiana, died Saturday after being left in a car for an "extended period of time," police Chief John Jester said. While it wasn't clear how hot it had been inside the car, temperatures in that community of 20,000 people reached 103 degrees. Greenfield is about 25 miles west of Indianapolis.

The baby's grandfather found the young girl and rushed her to the hospital, where she was pronounced dead. Her father, Joshua Stryzinski, was later arrested and charged with neglect of a dependent, resulting in death. Jester said that charge may change after detectives meet with prosecutors.

About 25 miles northwest, in the town of Fishers, Meg E. Trueblood was arrested Saturday for felony neglect of a dependent after her 16-month-old unattended daughter was pulled from a car at a shopping center, police said.

The temperature inside the vehicle reached 124 degrees, and the baby was inside for about an hour, said police spokesman Tom Weger. An officer broke a window to reach the child.

The girl was upgraded to stable condition Saturday night, and was released from the hospital Sunday to her grandmother, Weger said Sunday.