Why is there a heatwave in the United States?

As of Monday, June 24, a heatwave is impacting large parts of the United States due to the presence of a persistent heat dome. This dome, characterized by strong high-pressure systems, is currently centered over the central and southern United States (1)(2). Last week, the dome had previously hovered over the Ohio Valley and lower Great Lakes regions. That heat wave has begun to let up as of Monday.

There is also an excessive heat warning in effect for part of Southern California.

The National Weather Service warns that when combined with humidity, heat index values could soar to 110 degrees in some places, with little overnight relief.

A heatwave causes sinking air, which leads to warming temperatures and suppresses rain, exacerbating the heat. This phenomenon is exacerbated by human-caused climate change, which increases the likelihood, duration, and intensity of heatwaves.

Which cities or areas are affected by the heatwave?

Major cities and regions directly affected by the Gulf Coast, Midwest, and Central U.S. regional heat wave include:

• Dallas, Texas
• Jackson, Mississippi
• Jacksonville, Florida
• Kansas City, Kansas
• Little Rock, Arkansas
• Memphis, Tennessee
• Mobile, Alabama
• New Orleans, Louisiana
• Oklahoma City, Oklahoma
• Omaha, Nebraska
• Sioux City, Iowa
• Sioux Falls, South Dakota
• St. Louis, Missouri
• Tallahassee, Florida
• Topeka, Kansas

These cities and the surrounding region are expected to experience temperatures well above normal, with heat indices soaring into the triple digits in some places. The extreme heat poses significant health risks, especially to vulnerable populations.

There are also heat advisories and extreme heat warnings for the southern Central Valley in California and parts of Southern California, southern New Mexico, Utah, and Colorado.

How long will the heatwave last?

The current heatwave began recently and is expected to persist throughout first half of the week before shifting primarily to the South

Specific details on when it will end vary slightly by region.

Are there any alerts in place?

Yes, several alerts are in place due to the ongoing heatwave.

The National Weather Service has issued heat advisories and warnings across affected regions, including the Midwest, South, Upper and Lower Plains, and Southwest (3). These advisories warn of dangerously high temperatures and heat indices, urging residents to stay hydrated, avoid strenuous outdoor activities, and take precautions against heat-related illnesses.

Additionally, the combination of heat and dry conditions has increased the risk of wildfires in some areas.