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Around one hundred wildfires are burning across Oregon, California and Washington in the US.

Firefighters have been tackling the blazes for three weeks now.

Millions of acres of land and thousands of homes have been destroyed.

The destruction has forced thousands of people to flee their homes and some have lost their lives.

In Oregon firefighters are trying to get 16 large fires under control.

The smoke pollution from the wildfires has left the state's largest city, Portland, with the worst air quality in the world, according to IQAir.com.

There are a lot of reasons why the fires started, including lightening strikes.

However experts have said due to climate change we are seeing more extreme weather conditions. This does not affect the wildfires starting, but it does then help create the conditions for them to spread and become bigger.

Oregon, along with California and Washington, has seen extreme heatwaves in recent weeks, which provides ideal conditions for wildfires to spread.

Strong winds during the autumn season not only add to the drying out, but can spread embers and flames too.