An unrelenting heat dome continues to hover over the western United States this weekend, prompting heat alerts for tens of millions of residents.

Heat advisories and warnings were issued for 40 million Americans across 10 states on Sunday, with the highest temperatures concentrated in places like California, Nevada, Arizona and Utah.

Excessive heat warnings are currently in effect for cities like Las Vegas; Salt Lake City; Fresno, California; and Tucson, Arizona, where record stretches of dangerous temperatures are expected to continue for several days.

While heat alerts have been lifted in much of the Southeast, some remain in southeastern Texas and South Florida. It will still be hot elsewhere in the Southeast.

Record-setting temperatures plaguing the planet

The last 20 days on Earth have been the hottest 20 days on record, meteorology records show. The hottest day ever recorded in the northern hemisphere was measured on Saturday, when average temperatures reached 22.46 degrees Celsius -- or about 72.43 degrees Fahrenheit. The previous record, 22.18 degrees Celsius -- about 71.92 degrees Fahrenheit -- was set in summer 2022.

Several places in the U.S. broke records on Saturday as well. Palm Springs, California, hit 115 degrees on Saturday, breaking its record for consecutive days of 115 degrees, now nine days in a row. Temperatures are expected to drop closer to 110 degrees by Monday and through the week.

Phoenix broke a daily record on Saturday with a high of 118 degrees, continuing its record stretch with 23 consecutive days with temperatures at or above 110 degrees and six days in a row with temperatures at 115 degrees or higher. Sunday morning also continued the city's record stretch of 14 consecutive days of not dropping below 90 degrees.

When Las Vegas reached 115 degrees on Saturday, it broke a record set in 1937 at 114 degrees, extending its streak to nine days in a row at or above 110 degrees. The record for consecutive days above 110 degrees could be broken on Monday.

Tucson, Arizona, hit a daily record of 111 degrees on Saturday, shattering the record set in 2006 at 108 degrees. The city is now at eight days in a row at 110 degrees or above, tying with the record set in 2021. Tucson is also extending the record for the total number of non-consecutive days at 110 degrees or above, now at 14 days this year. The previous records were set in 1990 and 1994, at 10 days.

In El Paso, Texas, the record-smashing consecutive days of 100 degrees or higher is currently at 37 days, with no end in sight in the foreseeable future. The previous record was set in 1994, at 23 consecutive days.

On the East Coast, Miami has now had a heat index of 100 degrees or higher for a record 42 consecutive days, 10 days over the previous record of 32 set in 2020.

Alaska is also feeling the heat. The National Weather Service in Caribou is predicting the region's hottest month ever (of any month) for this July, with records going back to 1939.

Where will the heat be this week

The heat dome currently stationed over the west will move eastward toward the middle of the country this week.

While temperatures in the Midwest were below average last week, with highs in the 60s and 70s, the region will experience a summer wake-up call in the coming days.

Temperatures are expected to skyrocket in the 90s and 100s in places like Fargo, North Dakota; Lincoln, Nebraska; Kansas City, Missouri and Minneapolis this week. Some regions will experience heat indices of 105 degrees or more.

The heat will continue to blanket much of the U.S. through the end of July and into August, especially in the South.

Parts of the Great Lakes and Northeast may be spared by the extreme heat, with average or even below average temperatures forecast there for the start of August.