The McKinney fire in northern California has grown into the state's largest wildfire so far this year as climate change makes the blazes more commonplace and more intense.

Western Wildfires

A wildfire called the McKinney fire burns a hillside above her home in a national forest.

Associated Press

The fire spread to 51,468 acres on Sunday morning, just days after it started in rural Siskiyou County, California, located on the state's border with Oregon.

The Oak Fire, which started earlier this month and threatened the famous groves of sequoia trees, is the second largest wildfire in California this year.

Thousands of people have been ordered to leave their homes as the McKinney fire continues to burn.

The Pacific Crest Trail is a popular backpacking route in the country.

The governor of California declared a state of emergency in Siskiyou County on Saturday due to the McKinney fire and two other small fires.

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Heavy winds from the weekend caused the fire to spread fast. There is no known cause of the fire. Thousands of people have been forced to leave their homes and tens of thousands of acres have been burned this summer in California. Climate change has led to an increase in the number of fires in California.

The national parks are at risk of burning as climate change drives fires.

Here is how California protects its famous sequoias from fires.

Here is what we know so far about the fire. There is a magazine called "Forbes."