LAS VEGAS – Parts of Arizona, Nevada and Texas just experienced the hottest June on record, with the sweltering heat surpassing several long-standing records.

The broken records herald another summer of extremes – both in the United States and around the world – and offer a worrying outlook for the coming weeks and months, as July and August are typically the hottest months of the year in the Northern Hemisphere.

In Phoenix, with an average temperature of 36 degrees Celsius, it was the hottest June in the city's more than 100-year temperature record history, according to the National Weather Service.

Last month surpassed the previous record, set in June 2021, by nearly 2 degrees. Sky Harbor Airport in Phoenix recorded 14 days at or above 110 degrees in June, the weather service said.

The scorching heat has already taken its toll. There have been 13 heat-related deaths this year in Maricopa County, which includes Phoenix and many of its suburbs, and another 162 deaths are under investigation, according to the county's health department.

Last year, 645 people died from heat-related deaths in Maricopa County, a record high. It was a year of exceptional heat in the region. Last summer, Phoenix had 31 consecutive days of temperatures of 109 degrees or higher, ending an 18-day streak that began in 1974.

And July has already started off bumpy: 110 million people in 21 states are under heat warnings and observations for the Independence Day holidays.

Brutal heat was felt throughout the Southwest last month.

In neighboring Nevada, Las Vegas reached its own temperature record in June.

“No matter how you look at it, June 2024 was the hottest on record in Las Vegas,” the local National Weather Service office wrote on X on Sunday. The previous record was set eight years ago, in 2016.

Triple-digit temperatures were recorded nearly every day last month, the weather service said. The average temperature in June was 94.6 degrees, which was 7 degrees above normal and 1.8 degrees hotter than the previous record, according to the National Weather Service.

The heat also persisted, with the average high temperature being 41.4°C and the average low temperature being 28.4°C, meaning the city had little relief from the heat even overnight.

Due to climate change, heat waves are expected to become more frequent. Studies have shown that heat waves are becoming more frequent, longer and more intense with global warming.

But it's not just the new milestones that are noteworthy, the National Weather Service said.

“Even more impressive is how much we beat the old records,” the National Weather Service wrote on X, adding that the average high temperature in June beat the previous record by 1.2 degrees, a larger gap than between second and eighth place.

It was also a scorching June in West Texas. According to the National Weather Service, El Paso experienced the hottest June on record, breaking a 30-year-old record.

The average temperature in the border town reached 89.4 degrees, 0.4 degrees warmer than the previous record set in 1994.

Continued extreme heat is expected along the West Coast and parts of the South this week. Heat advisories and extreme heat warnings are in effect for the states of Washington, Oregon, California, Arizona, Nevada, Texas, Oklahoma, Missouri, Arkansas, Louisiana, Mississippi, Alabama, Tennessee, Kentucky, Georgia and Florida.

This article was originally published on NBCNews.com.