Record-breaking Heat Wave Sweeps Western U.S.
A powerful heat wave is demolishing records across the western United States.
Temperatures across the western U.S. are soaring to 20 to 30 degrees Fahrenheit above normal.
This week, North Shore, California, reached an astonishing 108 degrees Fahrenheit (42 degrees Celsius), equaling the state’s highest March temperature on record. The following day, Phoenix, Arizona, recorded 105 degrees F (41 degrees C), the earliest occurrence of such temperatures by over a month. Meanwhile, just outside Martinez Lake, Arizona, the temperature soared to 110 degrees F (43 degrees C), setting a new U.S. record for March.
An unprecedented heat wave is currently affecting the western U.S. A high-pressure system, the strongest ever recorded in the Southwest during March, has introduced this unseasonably high heat. Known as a ridge due to the upward curves in the jet stream it causes, this system extends over a vast portion of the U.S. and is expected to last several days, driving temperatures 20 to 30 degrees F (11 to 17 degrees C) above the norm. Climate scientist Daniel Swain remarked that it is “one of the more meteorologically exceptional events that I’ve seen in recent years in the American West, and that is saying something,” on his YouTube channel.
Record high temperatures in March usually occur toward the month’s end when it is typically warmer. However, this heat wave is so intense that it is surpassing some April records, let alone those for March. Swain described the event as “breaking records by … just absurd margins.”
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“This is a summerlike ridge occurring in March. It’s really genuinely shocking,” Swain added.
Ridges, flanked by low-pressure areas, cause surface air to flow from high to low pressure, allowing atmospheric air to descend and warm as it compresses. The stability under a ridge prevents cloud or rain formation, enabling sunlight to heat the surface directly.
Concurrently, a “Kona low” recently brought record rainfall to Hawaii. This weather pattern adds to the heat by releasing latent heat as water vapor condenses during precipitation. This moisture and heat are now moving to the Pacific Northwest, partly merging into the ridge and contributing to the warmth.
Climate change is also a factor. The World Weather Attribution research group suggests this heat wave would be “virtually impossible without climate change.”
In the past decade, events like this have become roughly four times more likely due to greenhouse gas-induced heat, making them up to 1.4 degrees F (0.8 degrees C) warmer than they might have been otherwise.
Heat advisories and extreme heat alerts have been issued across many western states to highlight the health risks, especially for the young, elderly, and outdoor workers. This is concerning not only due to the temperature itself but also because of the heat’s sudden onset, which does not allow the usual gradual acclimatization to warmer temperatures through spring and summer.
Read more: How to Keep Your Home Cool in Extreme Heat
There are fears the heat could worsen wildfire conditions. The West is experiencing various levels of drought, and the snowpack, which typically replenishes moisture in spring, is alarmingly low. The heat wave is expected to cause a rapid snowpack melt, potentially worsening drought and increasing wildfire risks as the seasons progress, Swain mentioned on his YouTube channel.
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