A sprawling heat dome, driven by a persistent high-pressure system that remained for more than a week, parked over North America and shattered temperature records across the United States. According to NOAA data analyzed by The Independent, March 2024 was the most abnormally hot month in the nation's history, with the average temperature soaring to 9.35°F above the 20th-century normal.
Along the southwestern border, the heat reached punishing levels, with Yuma, Arizona recording 109°F on March 20, a full 28 degrees above the 1991-2020 normal, according to official measurements. Across the border, Hermosillo, Mexico set a new March record of 108°F, officials reported.
Phoenix experienced historically early and intense heat: in 137 years of records, the city had never reached 100°F before March 26, yet temperatures this year soared past that mark weeks ahead of the usual early May milestone, researchers noted. The National Weather Service warned that the heat could intensify further, with highs possibly reaching 107°F.
Over time, the heat dome expanded eastward, putting much of the Midwest and Southeast under a prolonged period of record or near-record high temperatures. Lubbock, Texas sweltered through several days in the mid to upper 90s°F in late March, officials said. According to forecasters, the April heat wave that followed was exceptionally long for the time of year, challenging daily records over multiple days in dozens of cities.
In the Northeast, unusual April warmth pushed conditions closer to mid-summer, with New York City facing forecasts of 86–88°F, near the 87°F record set in 1941, according to multiple media reports. Philadelphia experienced even more extreme heat, with temperatures reaching 92–93°F and tying or setting all-time April records, according to the National Weather Service.
Across the entire country, the scale of heat was staggering as over 19,800 daily high temperature records were broken in March, data from multiple sources showed.
The heat was just one facet of an extreme weather pattern that, according to researchers, gripped nearly every region of the United States. The Palmer Drought Severity Index for March reached its highest level since records began in 1895, marking the third-driest month ever recorded, according to official data.
The warm winter and searing spring heat decimated the mountain snowpack in the West, a vital source of water for millions, according to officials. California's Sierra Nevada snow water equivalent plummeted to just 4.9 inches, or 18% of average, by early April, officials reported. More alarmingly, the Colorado River headwaters recorded a snow water equivalent of just over 4 inches, 24% of average and less than half the previous record low, threatening the water supply for 40 million people, officials warned.
According to the U.S. Drought Monitor, drought conditions tightened their grip, covering more than 61% of the contiguous U.S., the highest extent for this time of year since the drought monitor began in 2000, with some 97% of the Southeast and two-thirds of the West in drought. Adding to the peril, the vapor pressure deficit in the West, a measure of atmospheric thirst, was 77% above normal for the January-to-March period, the highest on record, scientists reported.
According to marine researchers, high ocean temperatures off the California coast raised fears of a 'Blob'-like marine heatwave, triggered by the same persistent high-pressure system. Globally, marine heatwaves are supercharging tropical cyclones, leading to a 60% increase in billion-dollar disasters from storms that pass over unusually warm water, according to recent reports.
After the blistering heat, a dramatic shift came as a polar vortex plunged southward, bringing a rapid cooldown. Temperatures in Minneapolis were forecast to drop near 0°F, with single digits in Chicago and teens and 20s across the Northeast, accompanied by snow. In Washington D.C., a record-breaking 86°F on a Wednesday was followed by snow on Thursday, the National Weather Service confirmed, illustrating the whiplash.
Severe storms and tornadoes tore through the Midwest, causing damage in Illinois and beyond, officials reported, while two storm systems dumped snow by the foot over northern Great Lakes states, forecasters said.
Health experts, citing the National Weather Service and AccuWeather, warned that early-season heat is a silent killer. People are not yet acclimated to high temperatures, making them more vulnerable, and heat remains the number one weather-related killer in the U.S., according to the National Weather Service and AccuWeather. A new study of six recent heatwaves found that all had periods that were non-survivable for older adults in full sun, and that previous wet-bulb temperature limits underestimate lethal conditions, according to the researchers.
According to officials and experts, the extreme drought and heat raised alarm bells over a potential wildfire crisis, with dry vegetation already primed for ignition. Water managers braced for cuts on the Colorado River, and ecologists noted unusual blooming of desert cacti, a symptom of the climate stress, setting the stage for a long and dangerous summer.
Despite the overwhelming data, the exact year of some reported events is disputed, though the majority of data points to March 2024.