A fast-moving bush fire - the size of 144 football fields - has forced thousands of Californians to flee, as a state of emergency is declared.
A major fire ravaged part of California on Sunday, as tens of millions of Americans baked in record-breaking temperatures.
Firefighters near Yosemite National Park were battling "hell on earth" over the weekend caused by one of the US state's largest wildfires this year.
The State's Department of Forestry and Fire Protection says the blaze has grown to nearly 48 square kilometres, knocking out power for some two thousand homes and businesses.
48 square kilometres is equivalent to approximately 144 football fields, and the flames are continuing to spread, with temperatures set to climb even higher amid a scorching heatwave.
The governor of Mariposa County declared a state of emergency on Sunday, after rescue services failed to quash the brush fire, which first broke out Friday afternoon near the town of Midpines.
More than a dozen US states are under heat advisory, with central metropolitan areas in the south, such as Dallas and Oklahoma City, expected to reach highs exceeding 38°C for at least the next five days.
A heat emergency is meanwhile in effect for cities up and down the northeast coast, stretching from Boston to Philadelphia and Washington.
The country's central and northeast regions are facing the brunt of the extreme temperatures, which are not expected to peak until Sunday and have sent public health officials scrambling.
In California, efforts to contain the flames have been frustrated by the hot weather, low humidity and bone-dry vegetation.
The Oak Fire has prompted numerous road closures including Highway 140, a major road into the National Park.
So far the flames have completely destroyed 10 residential and commercial buildings.
Daniel Patterson, a spokesperson for Sierra National Forest says 6000 people living across the sparsely populated terrain have received orders to evacuate.
The high temperatures, which are due to global warming, have already caused an uptick in emergency calls for heat-related illnesses.
California has experienced increasingly larger and deadlier wildfires in recent years as climate change has made the west of the US much warmer and drier over the past 30 years.
Scientists have said extreme weather events will continue to become more frequent, destructive and unpredictable unless governments and people drastically cut their carbon emissions.
“The fire is moving quickly. This fire was throwing embers out in front of itself for up to 2 miles yesterday,” Patterson said. “These are exceptional fire conditions.”
The cause of the fire is under investigation.
Cities across the US have opened cooling stations and increased outreach to at-risk communities such as the homeless and those without access to air conditioning.
This comes as US President Joe Biden is considering announcing a climate emergency which will help push his renewable climate agenda through Congress, where it is currently blocked.