Extreme heat warnings in effect in 28 states across US

The National Weather Service has warned that extreme heat will affect more than 100 million people in the US this week, with triple-digit temperatures in some states and broken temperature records in many areas across the country.

Heat warnings and advisories have been put in place for 28 states, with central and southern states facing the brunt of the scorching heat.

Some parts of Oklahoma reached 115F (46C) this week, while the Dallas area hit 109F (42C).

In the north-east, where temperatures are settling in at more than 90F (32C), city leaders have warned residents to limit outside activity during the hottest times of the day.

Additional reporting by Nina Lakhani