The United States is facing a potentially staggering expansion of dangerous heat over the coming decades.

This analysis shows the rapid, widespread increases in extreme heat that are projected to occur across the country due to climate change, including conditions so extreme that a heat index cannot be measured. The analysis also finds that the intensity of the coming heat depends heavily on how quickly we act now to reduce heat-trapping emissions.

The results highlight a stark choice: We can continue on our current path, where we fail to reduce emissions and extreme heat soars. Or we can take bold action now to dramatically reduce emissions and prevent the worst from becoming reality.