A serious weather alert has been issued for millions of people across parts of the United States, with officials advising residents to remain indoors this weekend as extreme heat spreads across the country.

A strong heat dome is moving over the Southwest and into central states, trapping hot air beneath it. Instead of normal spring temperatures, many areas are facing conditions that feel more like the middle of summer.

Meteorologists say this happens when a large high-pressure system blocks cooler air from entering. The trapped heat builds day after day, causing temperatures to rise well above seasonal averages.

Several states are already seeing record-breaking heat levels. Authorities are particularly worried about older adults, outdoor workers, and people who do not have dependable access to air conditioning.

Emergency officials are asking people to reduce outdoor activities, drink plenty of water, and check on family members and neighbors who may be more vulnerable during the heatwave.

The extreme temperatures are also creating other problems. Power grids are under pressure as energy use increases, while dry conditions are raising wildfire danger and causing concern for farmers as soil dries out quickly.

Experts warn that heat events like this are becoming stronger and more common due to long-term climate changes. With more than 20 states affected, officials are urging everyone to take the warnings seriously and avoid unnecessary travel during the hottest parts of the day.