Nearly every type of wild weather hit some part of the United States on Monday, as normal changing seasons were met by cold and warm air colliding along a jet stream that meteorologists described as behaving unusually. In a single day, the country saw a blizzard around the Great Lakes, damaging high winds across much of the East with threats of tornadoes, and then a push of Arctic cold. The outlook also included a heat wave poised to take hold in the Southwest and continued heavy rain in Hawaii, amid drought that persisted in more than half the nation.
The extremes came together across different regions, with meteorologists also noting that hurricanes were the only major extreme-weather category “missing” from the mix and that it was the wrong time of year for that. They said parts of what observers saw on weather maps looked more like June or July than mid-March.
AccuWeather meteorologist and Vice President of forecast operations Dan DePodwin said the timing itself was striking, adding: “We really have most types of extreme weather across the U.S. here in mid-March.” He and other meteorologists said that while most of the individual extremes could occur in spring, the specific exception was a developing heat pattern in the Southwest that was expected to be record-shattering and resemble summer more than March.
Climate Central Chief Meteorologist Bernadette Woods Placky said the overall combination was unusual, but not unprecedented for the season. “It is unusual for everything to be at the absolute extreme levels that they’re experiencing right now, but it is not completely unusual in spring to see wild weather happen,” she said.
Multiple forecasters described how springtime physics can set up this kind of pattern. Dan DePodwin said the clashes between air masses are most likely in February or March or maybe early April, when warmer air is drawn north as the sun moves closer to the equator, leading to more frequent confrontations between extreme air masses. In that setup, he said, strong winds—March being the windiest month—can form, and moisture can help trigger severe storms, with enough cold available for winter-style storms to still reach places such as the Great Lakes.
Meteorologists also pointed to a “wacky shaped jet stream,” describing it as the river of air that moves weather from west to east on a path with major swings. Jennifer Francis, a climate scientist at the Woodwell Climate Research Center on Cape Cod, said: “The positions of the enormous northward and southward swings in the jet stream are likely being influenced by the strong ocean heat waves in the northwest Pacific, around Baja, and along the Atlantic seaboard, which are fueled by human-caused climate change.” She tied those ocean conditions to the broader backdrop of climate change.
The AP report also referenced research by University of Pennsylvania climate scientist Michael Mann, saying his study showed changes in planetary waves increasing in a warmer world between April and September, though he said extending the pattern into March was “a bit more speculative.” Woods Placky said the overall mid-March mix had some climate-change “fingerprints,” but that the greenhouse-gas influence was not expected to be nearly as strong as for the most intense heat that was forecast later in the week.
In Hawaii, the downpours were described as being associated with a Kona low pressure and were said to be fed by unusually warm Pacific waters, which Woods Placky linked to the jet-stream pattern and the broader warmth. Forecasters also highlighted what they said was the next phase: the most significant extremes would arrive in a day or two, when a strong high pressure system—or heat dome—parked over the Southwest.
That coming heat was highlighted with comparisons to past March conditions. The report said Phoenix has only once had a March day reach 100 degrees (37 Celsius) and typically does not see 100-degree days until May, but forecasts called for five straight days of triple-digit temperatures flirting around 107 (41 Celsius) or higher. It noted that the hottest March day in the United States on record was 108 (42.2 Celsius), set in Rio Grande City, Texas, in 1954, and said there was a good chance the record could be tied or broken.
Jeff Masters of Yale Climate Connections described the level of the heat as something that could not have been produced in the same way without human-caused warming. He said, “This is the type of extreme heat that you could not get without human-caused climate change,” adding, “The extremity is so ridiculous that 50 years ago you would not have seen it.” The AP report also included a remark from a weather service forecaster who wrote that when he looked at forecast temperatures from a computer model, “I audibly gasped.”
With drought already covering much of the country, Masters said he worried that the heat could contribute to fires like the one blazing in Nebraska, and he warned of a challenging fire season in the West. “We’re going to see an early and severe fire season out West,” he said.