July-September Outlook: Coolest Summer Since 2017, But Central US Likely To Be Hotter Than Average

T​he rest of summer into early fall might trend hotter for some, but it could still end up being one of the nation's coolest summers in years.

Temperatures are expected to be warmest relative to average in the country’s midsection from July through September with risks for cooler weather mainly near the West Coast, according to the latest outlook from The Weather Company, an IBM Business, and Atmospheric G2.

B​ut El Niño could affect that scenario, potentially leading to a cooler rest of summer in parts of the nation's central and northern regions.

"Combining June with the July/August forecasts ... gives the coolest summer since 2017," said Dr. Todd Crawford, Vice President of Meteorology at Atmospheric G2 and author of the outlook.

July Outlook

The bulk of the hotter than average temperatures may be from the Northern Plains into the Great Lakes in July. Parts of New Mexico and West Texas are also expected to be hotter than usual.

On the other end of the spectrum, a cooler than typical July is most likely in parts of California and Nevada. Parts of the East Coast from Virginia to the Carolinas could also trend slightly cooler than average.

August Outlook

The heat is expected to be more expansive from parts of the Rockies into the Northern Plains and upper Midwest in August. However, odds favor a hotter than usual August from the Desert Southwest to much of the rest of the Midwest.

The East Coast may remain near average or slightly warmer while the West Coast could skew slightly cooler as summer comes to a close.

"​We still think August will be the warmest month of summer, relative to normal," said Crawford.

September Outlook

A​ hotter than usual September is most likely from New Mexico and Texas to the central Plains and Midwest. However, much of the U.S. from the Desert Southwest and Rockies eastward is expected to have a warmer than average September.

Once again, only the West Coast and perhaps the northern Rockies may skew slightly cooler than usual.

The El Niño Wild Card

Ocean temperatures in the central and eastern Pacific have now climbed above the threshold (0.5 degrees Celsius above average) for El Niño, NOAA declared in early June,​ and is expected to last through next winter.

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.

T​hat adds significant uncertainty to the July through September outlook.

A​t the time this outlook was issued, most dynamical climate models suggested much of the country would be hotter than usual through September.

H​owever, past years with similar El Niño trends and intensities were markedly cooler from July through September in the Plains, Midwest and East.

"While we've favored the dynamical models for now, we are still barely above the 30-year normal for July, and there may even be some downside left," said Crawford, referring to the potential for cooler adjustments to the outlook going forward.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.