US set for sweltering Independence Day with 137m people under heat alerts

Temperatures set to soar on Thursday and into weekend, with record highs possible and little chance of relief

The stage is set for an explosive Fourth of July across the US, and not just because of Independence Day revelry.

More than 137 million people in 21 states were under heat alerts on Wednesday afternoon, as a brutal and potentially historic heatwave sent temperatures soaring throughout the holiday with little chance of relief over the next week, even after the sun sets.