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Heat wave enveloping West will shatter records, spark wildfires

A dangerous and widespread mid-June heat wave is bringing blowtorch-like heat, skyrocketing power demand, and “critical” wildfire danger to much of the West Tuesday through this weekend.

Why it matters: The heat is building in a region that is experiencing a record drought, leading to dangerous fire weather conditions, straining electrical grids, and causing water supplies to dwindle further. The heat itself may prove deadly.

Threat level: While the Southwest in particular is used to hot weather, this event could break all-time records in normally hot places like Las Vegas, where the all-time high temperature of 117°F could be toppled and overnight low temperatures won’t fall below 90°F for several days.

  • The heat wave has engulfed regions from New Mexico to California, northeastward to Utah, and all the way north to the Canadian border, with temperatures approaching the century mark Tuesday in Wyoming and Montana.

Details: Heat warnings and advisories are in effect for tens of millions.

  • Death Valley, Calif., which holds the U.S. record for hottest temperature ever recorded, could eclipse 120°F for several days.
  • In addition to the Las Vegas record, statewide high-temperature records for Arizona (128°F), set in Lake Havasu City, and Nevada (125°F), set in Laughlin, could be in jeopardy.
  • California’s Central Valley region is likely to see temperatures in the triple digits throughout the week, and even downtown Los Angeles could experience triple-digit heat on Tuesday. Areas in the San Diego, L.A., and San Francisco metro regions could see triple-digit heat lasting much of the week.
  • “Critical” fire weather conditions are forecast for Tuesday night in Santa Barbara County, as well as portions of Nevada, Utah and Montana. Vegetation is at record-dry levels across many parts of the West amid an extreme drought.
  • More than 20 large wildfires are already burning in Arizona, California and other parts of the West.
  • In Utah, where temperatures in Salt Lake City are expected to be hover near 110°F Tuesday, Weather Service forecasters urged residents to “[p]lease take measures to reduce the impact of extreme heat on yourselves and your neighbors.”
Weather map showing record heat, in red colors, across the Southwest.
Forecast high temperatures on June 17, 2021, with boxes indicating record highs. (Weatherbell)

By the numbers: The National Weather Service forecast office in Las Vegas is warning of significant threats to life and infrastructure from Tuesday through Saturday as the heat builds and refuses to relent.

  • NWS forecasters noted Monday that the last time heat of similar magnitude and duration occurred there was late June to early July 2013: “During that event, Southern Nevada saw nearly 30 fatalities and over 350 heat-related injuries as well as temporary power outages.”
  • Las Vegas has only seen a five-day stretch of maximum temperatures at or above 113°F five times since instrument records began there in 1937, the Weather Service said.
  • Three of the five occurrences have been since 2005, an indication of the climate change-related warming trend there.
  • In Sacramento, Calif., high temperatures could reach 110°F by Thursday as heat builds across the heart of the Golden State’s parched agricultural belt.

Between the lines: The heat will raise power demand at a time of decreased output at hydroelectric plants. It will also dry soils further, expanding the area of “extreme” to “exceptional” drought, the worst categories.

  • Already, Lake Mead, the nation’s largest reservoir by volume, has hit its lowest level on record. This heat wave is likely to evaporate more water.
  • California officials have secured more electricity supply to be brought into the state during heat waves this year, after rolling blackouts were imposed in 2020. But regional heat waves like this one will strain the grid by making importing power from other states more difficult.
  • So far, the Cal ISO, which operates the state’s grid, does not plan to implement rolling blackouts or flex alerts to encourage residents to conserve power, though that could change.
  • ERCOT, the Texas grid operator, asked residents to cut back on power use Monday and Tuesday as several power plants were down just as temperatures climbed. The total amount of generation outages is about 11,000 megawatts, much higher than average at this time of year.
  • Power demand may spike to a June record amid triple-digit heat and high humidity, ERCOT warned.

Context: The heat wave and drought are reinforcing one another. Given the dryness, more solar radiation can go into heating the air, rather than evaporating moisture in soils. This vaults air temperatures higher.

  • One of the most robust conclusions of climate science is that heat waves are becoming more intense and longer-lasting as the climate warms overall.
  • In recent years, there has also been a trend toward stubborn and sprawling areas of high pressure aloft, known as heat domes, that block storm systems and keep hot weather locked in place for days at a time.
  • This heat dome extends from the U.S.-Mexico border to the Canadian border.