Climate Change Made US West Heatwave ‘Nearly Impossible’ in Past, Scientists Say

Millions of people across regions stretching from the Pacific coastline to the Rocky Mountains have been exposed to unusually high and potentially dangerous temperatures, with readings reaching up to 30°F (17°C) above seasonal norms.

Researchers say the climate crisis—largely driven by the continued use of fossil fuels—has significantly increased the likelihood of such extreme heat events. A rapid study released on Friday found that similar heatwaves are now four times more likely to occur than they were just a decade ago.

Ben Clarke, a climate researcher at Imperial College London and co-author of the analysis, described the current conditions as highly abnormal for this time of year, noting that temperatures of this magnitude are far beyond typical March levels.

The findings were produced by World Weather Attribution, an international group of scientists that examines the role of climate change in extreme weather. According to the study, a comparable heatwave in 2016 would have been noticeably less intense, with temperatures around 1.4°F (0.8°C) lower than those seen today.

Friederike Otto, another contributor to the research, emphasized that the results clearly demonstrate how global warming is pushing weather patterns beyond historical limits. She stated that such extreme conditions would have been unimaginable before the industrial era.

To assess the event, scientists analyzed forecast data for a five-day period between 18 and 22 March. They combined real-time weather observations with climate model simulations to evaluate how rising global temperatures have altered the intensity and likelihood of such heatwaves.

The current extreme heat has been linked to a persistent high-pressure system, often referred to as a “heat dome,” which traps warm air over a region. This system has already broken temperature records in more than 140 cities, from California to Missouri, according to meteorological data. States including California, Nevada and Arizona have issued warnings due to the severity of the conditions.

Forecasters expect the heat to intensify further in the coming days, particularly across the southwestern United States, before spreading toward central and southern regions. By the end of the week, as many as 100 cities could record their highest March temperatures on record.

Authorities have warned that extreme heat remains the deadliest type of weather hazard in the United States. Officials are increasingly concerned about rising cases of heat-related illnesses, especially among vulnerable populations such as the elderly, outdoor workers and those without access to air conditioning. Residents have been advised to stay hydrated and limit outdoor activity.

The heatwave is also affecting local economies. In California and the Lake Tahoe region, several ski resorts have been forced to close early or scale back operations due to rapid snowmelt and unseasonably high temperatures.

Experts warn that these events highlight a broader shift in climate patterns. Otto noted that seasonal norms that once defined life in the western US are rapidly disappearing, putting both ecosystems and communities at risk. She stressed that the impacts of climate change are no longer distant threats but are already unfolding, calling for urgent policy responses to match the growing reality.