A sudden and intense heat wave is spreading across the United States, bringing unusually high temperatures far earlier than expected. What began in the Southwest is quickly expanding, pulling millions into conditions described as “almost summer-like.”

Meteorologists warn that up to 23 states could be affected by a powerful “heat dome,” with temperatures rising as much as 30 degrees above normal. Areas that usually experience mild spring weather are now facing extreme heat, creating a sharp and unexpected shift.

The system started in states like California, Nevada, and Arizona, and is now moving east toward Texas, Kansas, Missouri, and beyond. A “heat dome” works by trapping hot air under high pressure, blocking clouds and allowing the sun to intensify conditions without relief.

In some regions, temperatures may exceed 100°F, breaking long-standing records. Even typically cooler areas, such as parts of the Midwest, could see temperatures jump into the 80s—far above what’s expected for this time of year.

Officials are also warning about added dangers. The combination of heat and dry air increases the risk of wildfires, prompting hazardous weather alerts. With dozens of cities already breaking records, the situation highlights how quickly conditions can escalate, leaving many unprepared for the sudden and extreme change.