Low water levels are visible next to houseboats anchored at Bidwell Canyon Marina on Lake Oroville on June 01, 2021 in Oroville, California.

Justin Sullivan | Getty Images

Almost three-quarters of the western US is grappling with the worst drought in US Drought Monitor history, as hot and dry conditions will increase the risk of forest fires and water scarcity this summer.

Parts of California, Nevada and Washington saw stifling triple-digit temperatures last week amid the drought, according to the National Weather Service, with states issuing excessive heat and heat warnings in some areas.

Conditions this spring are much worse than they were a year ago. In fact, nearly half of the continental US is experiencing a moderate to exceptional drought, which is the most significant spring drought in the country since 2013, according to scientists from the National Oceanic and Atmospheric Administration.

The U.S. Drought Monitor, a map created by a team of scientists and government scientists, was launched about two decades ago. It is updated every Thursday to show the location and intensity of the drought across the country.

An aerial photo on June 1, 2021 in Oroville, California shows the remains of a house and trees that were burned by a recent forest fire near the steep banks of Lake Oroville.

Justin Sullivan | Getty Images

In California, which is frequently hit by droughts and massive forest fires, state reservoirs are 50% lower than they should be at this time of year, an Associated Press report said, which could result in hydropower plants during the worst possible time switched off during the forest fire season.

The state had its worst forest fire season last year in terms of total acres burned, fueled in part by prolonged heat waves, drought and lightning strikes made worse by climate change.

During a meeting with the California Department of Forestry and Fire Safety chief in Sacramento last week, Governor Gavin Newsom called for a record $ 2 billion budget to prepare for forest fires and expand his fleet of aircraft to fight the fires.

California will also have its largest fire department in history operating on-site during the main fire season.

Alisha Herring, a communications officer for Cal Fire, told CNBC the department has completed dozens of fuel reduction projects, including controlled burns, to reduce the risk of fire this season.

“If we get deeper into the summer months, the conditions will only dry out further, increasing the risk of fire,” she said. “These arid conditions make it a lot easier for wildfire to ignite and burn hotter and faster than we would normally see at this time of year.”

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Farmers in the northwest are also grappling with increasing drought damage to crops and having difficulty irrigating fields when the water level drops.

“72% of the western US is currently in a ‘severe’ drought or worse. This is now the largest severe drought in recorded history,” climate scientist and activist Eric Holthaus wrote in a tweet. “We are in a climate emergency.”

Climate change makes droughts and other extreme weather conditions such as hurricanes and forest fires more frequent and intense.

Researchers also say that rising temperatures have pushed the American Southwest into a decade-long mega-drought, which has resulted in a decline in snow cover, lake and river levels, and groundwater availability, among other things.

“After two years of water in arid conditions, both California and Nevada are now 100% dry,” said an update to NOAA’s National Integrated Drought Information System on Friday.

“And given the dire drought conditions, rapidly decreasing snow cover and low reservoir levels, concerns about the forest fire season are growing,” it said.