Warnings for millions of people are being issued as the temperature continues to increase.
The dangerously high temperatures that have been affecting major cities across the United States pose a greater threat to certain groups of people than to others.
According to the Centers for Disease Control and Prevention (CDC), around 600 people each year are killed in the United States due to extreme heat. However, campaigners estimate that roughly half of those killed were homeless.
In the United States, the number of deaths caused by heat exceeds the number of deaths caused by hurricanes, floods, and tornadoes combined.