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The rapid onset of El Niño could result in a cooler and wetter summer compared to last year, especially at the onset of the warmer months.
Temperatures are expected to be warmest relative to average in the country's midsection from June through August with risks for cooler weather on the East and West coasts, according to the latest outlook from The Weather Company, an IBM Business, and Atmospheric G2.
But the fly in this forecast ointment may be a cooler start to summer - particularly in the Southwest and possibly into the South.
"T?his summer could be the coolest since 2017," said Dr. Todd Crawford, Vice President of Meteorology at Atmospheric G2 and author of the outlook.
As alluded to above, the risk for cooler-than-average temperatures this summer is highest in June and across much of the Southwest. Near-average or slightly cooler temperatures are possible across much of the country's southern tier.
Climate models continue to suggest that heat will remain focused in central Canada and into the northern United States. Since the last outlook, this forecast heat has increased in likelihood from Washington state into the Dakotas.
The bulk of the heat will spread southward into the Plains and Four Corners in July. This could be a fairly substantial warmup from June in the southern Rockies and Southern Plains.
Portions of the coasts could remain near average or slightly cooler, particularly in Southern California.
The heat will remain in place and potentially intensify from the Plains into the upper Midwest.
The Northeast and West Coast could remain near average or slightly cooler as summer comes to a close.
After a multi-year cooling in the Pacific, temperatures in the central and eastern Pacific have now climbed to the threshold (0.5 degrees Celsius above average) needed to be considered for an El Niño. For an El Niño to be officially declared, that anomaly must persist for three months, which is almost certain to occur this summer or early fall.
El Niño is an oceanic warming and atmospheric response to that warming which frequently causes months- to years-long changes in temperature and precipitation around the world.
This change "will favor a continuation of ridging across northwestern U.S. and southwestern Canada by summer with cooler outcomes across the eastern U.S.," according to Crawford.
Years with similar El Niño intensities resulted in widespread cooler temperatures across the Great Lakes and East, but Crawford noted, "We are hesitant to go too cool given the strong summer warming trends in recent decades."
Additional cooler forecast changes could be made into the summer months.
El Niño-like conditions will likely result in wetter-than-average conditions across the South and East as well, which would tend to keep temperatures from becoming too hot.
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