50 million remain under a heat advisory this weekend.

Millions of Americans will still be under a sweltering heat wave the rest of this weekend and into much of next week that the National Weather Service described as “oppressive” and “dangerous.” About 50 million people in the nation are under heat warnings or advisories, Frank Pereira, a meteorologist with the Weather Service said in an interview on Saturday.

The heat, which encompassed most of the Central Plains and the Southeast earlier this week, moved west, according to meteorologists. Most of the advisories were issued in parts of Arizona, Texas and Alabama.

Heat index figures in Texas are averaging around 110 to 114 degrees in some places. Local reports suggested that the power grid in Texas, which has failed in previous heat waves and natural disasters, could be at its breaking point.

Into the weekend, much of Central and South Texas, along with the Mississippi Valley, will see temperatures in the triple digits, Mr. Pereira said. The Southeast, which had been suffering under a “heat dome” for much of the week, will finally get a respite.

The most anomalous heat Saturday, Mr. Pereira said, will be in portions of northeastern Colorado and northern Kansas and stretch all the way up into North Dakota.

The average heat indexes in most of those areas would be well into the 90s and low 100s in some places, he said.

Places like Phoenix could see highs above 110 degrees over the weekend. On Monday, the city could see a high of 116, an extreme temperature even for the area, the Weather Service said.

Memphis broke a heat record on Friday when it reached 103 degrees. Its previous record was 101 from 1980 and 1969.

A potential cold front could alleviate the heat next week, Mr. Pereira said, “but it’s still going to remain quite warm, well above average, all the way from the southern plains to Texas and Oklahoma.”