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Western areas of the United States are experiencing an extreme heatwave, with forecasts of record-breaking temperatures in the states of California and Nevada.

It comes just weeks after another dangerous heatwave hit North America.

The region has experienced the hottest June on record and California's Death Valley recorded a high of 54.4C (130F) on Friday.

Forecasters say Las Vegas's record of 47.2C (117F) could also be passed.

The National Weather Service has advised the millions of people affected to drink plenty of water and stay in air conditioned buildings.

The heatwave has left huge areas of California extremely dry which has led to many wildfires.

Firefighters battling the blazes say the air is so dry that much of the water dropped by aircraft to put out the flames evaporates before it reaches the ground.

A lot of people have been struggling to cope with the rise in temperatures and have become ill because of it.

Officials are trying to help locals to stay cool, giving them advice on how to look after themselves and their pets during the hot weather and setting up places where they can cool down.

In Idaho, Governor Brad Little declared a wildfire emergency and the National Guard has been helping to fight fires also sparked by lightning.

In the north of Nevada, near the border with California, people were evacuated from their homes as wildfires triggered by lightning strikes tore through parts of the Sierra Nevada forest region.

The fire was also threatening power cables that send electricity to California.

Power grid operators in California have urged customers to conserve electricity by reducing their use of appliances.

Experts say that climate change is expected to increase the frequency of extreme weather events, such as heatwaves but linking any single event to global warming is complicated.

However, a study by climate researchers said the heat that hit western Canada and the US at the end of June was "virtually impossible" without climate change.