South-west and parts of the west hardest hit amid warnings to ‘take heat seriously’ as forecast in Phoenix to rise to 118F Sunday

More than 100 million people, around a third of Americans, were under extreme heat advisories this weekend, with officials warning conditions could get worse in Arizona, California and Nevada and that record-breaking heat was expected to continue into the new week.

The south-west and parts of the west were the hardest hit with a warning to residents on Sunday to “take the heat seriously and avoid time outdoors” by the National Weather Service which said it was “potentially deadly to anyone without effective cooling and/or adequate hydration”.