The heat is on this summer, and it's forecast to stay that way.
Millions of Americans had already been given a taste of sweltering temperatures by the time the summer solstice -- the longest day of the year and the official start of the summer season -- arrived last week.
A reprieve from the heat is likely not coming, forecasts into the coming months show.
Following back-to-back dangerous heat waves that impacted a large swath of the nation over the past two weeks, much of the country will be bracing for more rounds of intense heat as summer continues.
The final days of June and first days of July will likely bring above-average temperatures along the Gulf Coast, with building heat in the West. Rounds of intense summer heat and longer-duration heat waves will be likely over the next couple of weeks and heading through the month of July, according to long-range weather forecast models monitored by meteorologists.
Odds favor above-average temperatures across much of the South and along the East Coast, according to the latest July outlook issued by the National Oceanic and Atmospheric Administration's Climate Prediction Center. While there will be breaks in the heat from time to time, more rounds of prolonged, dangerous heat will be more likely in these areas -- which have already experienced triple-digit temperatures -- heading into the middle of summer.
The Midwest, which saw some of the highest temperatures during the most recent heat waves, will be one of the few regions to experience relief from the heat in the coming days.
Heat is the No. 1 weather-related killer. On average, more people in the U.S. die from extreme heat than any other severe weather event, including tornados, hurricanes and flooding combined, according to the National Weather Service.
Vulnerable populations, including impoverished and marginalized communities and those with pre-existing health conditions such as asthma and heart disease, are most at risk when temperatures begin to skyrocket, Ladd Keith, an assistant professor in the School of Landscape Architecture and Planning at the University of Arizona, told ABC News.
"With climate change, we've already seen the number of heat waves increase," he said. "In the 1960s, they were occurring twice per year. And we've already seen that increase to six times a decade in the last decade."
As the heat index increased, cities all over the country began offering heat management strategies such as cooling and hydration centers. In Tennessee, utility company Middle Tennessee Electric even suspended disconnections for non-payment until at least July 6 amid the forecast for scorching temperatures.
Cities tend to be hotter than their natural surroundings because of the heat island effect caused by buildings, roads and other infrastructure, which absorb and re-emit the sun's heat more than a natural landscape, Keith said. This is why is it important for cities to also implement heat mitigation strategies, such as planting trees, increase vegetation, and use cool pavements and cool roofs during new construction, he said.
"Just the average temperatures that are rising due to climate change -- and how we built our cities -- can expose people to unsafe temperatures throughout the summer season, particularly for historically hotter states," Keith said. "And so that's a concern, because it could certainly lead to things like dehydration, heat, heat exhaustion and up to heatstroke."
Heat severity in urban areas is "drastic and inequitably distributed," Keith said. Lower-income, marginalized minority neighborhoods are physically hotter because they have less vegetation, and they have less public investment that's historically connected to those locations, he added.
In addition, a lot of critical urban infrastructure and systems, such as industry, airports and transportation hubs, are typically located in lower-income areas "intentionally," Keith said.
"So that physically makes those places hotter, so they're exposed to more heat just by where they live," he said.
Combine that with the inability to access health care or afford basic utilities such as air conditioning, and people's health can succumb to the heat, Keith said.
The heat and megadrought are becoming such a concern in the West that the city of Los Angeles named its first-ever chief heat officer earlier this month, while the Federal Emergency Management Agency has identified Los Angeles County as the nation's most vulnerable county to heat waves.
Despite cities being hotter, there are actually more heat-related hospitalizations in rural regions, likely due to the types of occupations those residents hold and their travel patterns, Keith said.
The next heat wave is forecast to also hit the Pacific Northwest, a region that experienced triple-digit temperatures twice in 2021 -- something that would have been unheard of two decades ago.
It is estimated that about 1,400 people in the U.S. and Canada died as a result of that heat wave.
"There's just a less visible risk, and it kind of hides some of those deaths, unfortunately," Keith said.