A stunning heatwave that shattered records in the US west is threatening to rapidly melt the sparse snowpack and ramp up wildfire risks in the seasons ahead.
March has already been historically hot, but the early onset of summer weather across the region may be here to stay. There’s little reprieve in forecasts, which show more heat records may fall this spring.
Extreme heat is exceptionally dangerous, especially so early in the year, when bodies and systems are not prepared for it and when it lingers over a long period of time. This heatwave is also posing significant threats to the water supply. After one of the warmest winters in the west, the snow that feeds streams, reservoirs and soil moisture as it melts through the summer season is already dismally scarce in key watersheds.
“Anomalous warmth and historic snow drought will still lead to ecological and wildfire-related impacts as soon as this spring, and possibly wider water challenges by late summer and beyond,” climate scientist Daniel Swain said in a post about the heat.
His primary concern is in the interior west, especially the Colorado River basin, which could face “water supply and hydroelectric shortfalls, an early and intense fire season, and ecosystem degradation”.
“This is a big deal,” he added.
The unprecedented heat event pushed temperatures between 20 to 30F higher than average across the region, with some areas seeing spikes up to 40F higher than normal.
March high temperature records have already been broken in at least 14 states. A new national temperature record for the month was smashed last Thursday, when an area in Arizona hit 110F (43.3C). The record didn’t stand long; by Friday, it was broken again, when a parts of California and Arizona reached 112F (44.4C). The record is just one degree shy of April’s heat record.
More than 400 daily records were broken last Thursday when the heatwave peaked, caused by a large and persistent dome of pressure settling over a large swath of the west. But “this is not going to be a heat event that suddenly goes away”, Swain said. “We are still going to be experiencing record warmth and dryness next week – at least for the next seven to 10 days.”
Hundreds more high-temperature records might be breached this week, according to forecasters, as the extreme heat pushes east.
“High temperatures are forecast to reach 20-25 degrees above average,” forecasters with the National Weather Service said in an update Monday, noting that there’s potential to break numerous records through the south-west, inter-mountain west and into the central US.
The heatwave has eaten away more of an already deeply depleted snowpack, needed to sustain the thirstiest states through the drier months.
This scorching spring started on the heels of a record-warm winter for nearly every major river basin in the west, according to the federal drought monitor, thrusting the region into a snow drought even before temperatures spiked. Measurements of water amounts frozen within the snow were below the median at 91% of western stations by 8 March.
By mid-March, more than half of the continental US had already been classified in moderate to exceptional drought conditions.
“Drought conditions worsened or developed for much of the Great Plains, Lower Mississippi Valley, and south-east US due to warmer and drier than normal conditions this winter,” said Jon Gottschalck, chief of the Operational Prediction Branch at NOAA’s Climate Prediction Center, in a spring outlook published on Friday. The agency said drought is expected to persist and expand across the west due to the unrelenting heat.
Heat also bakes more moisture out of landscapes, amplifying wildfire risks and extending the seasons when ignitions can quickly become infernos.
The hot, dry conditions are fueling an explosive start to the high-risk wildfire season, and vegetation is becoming increasingly primed to burn.
“With fuel moistures trending near record lows for this time of year, similar conditions could support fast-moving fires and new large fire activity when winds align,” officials with the US National Interagency Fire Center wrote on Friday. More than 1.4m acres have already burned this year, more than double the 10-year average for the same period, driven largely by big blazes that erupted in Nebraska this month.
Two fires in the state spread across more than 800,000 acres, chewing through parched grasses. The Morrill fire in west-central Nebraska grew to more than 640,000 acres alone, making it the largest in the state’s history. The blaze was at 98% containment on Monday.
An analysis by World Weather Attribution, an international consortium of climate researchers, found that the intense heat impacting the region would be impossible without the climate crisis and signals the dangers of what’s to come.
“These findings leave no room for doubt. Climate change is pushing weather into extremes that would have been unthinkable in a pre-industrial world,” Friederike Otto, a climate science professor at Imperial College London, previously told the Guardian.
“In the US west, the seasons that people and nature were used to for centuries are disappearing, putting many, including outdoor workers and those without air conditioning, in danger,” he added. “The threat isn’t distant – it is here, it is worsening and our policy must catch up with reality.”
