Fall is a season of transitions: brutally hot summer days give way to crisp fall evenings, green leaves take on colorful hues and fresh summertime flavors are drowned out by the warmth of baking spices.
But while pumpkin spice is already overtaking the country, the familiar fall feel may take much longer to materialize as the warmth of an intensely hot summer in the United States shows signs it could bleed into the new season – a trend as the world warms from fossil fuel pollution.
“The fall season is increasingly being seen as an extension of summer,” said Jennifer Marlon, a climate scientist at the Yale School of the Environment. “It’s warming fast.”
Intense, frequent and long-lasting warmups will likely make this summer the hottest on record for nearly 100 cities in the West, South and East, including Las Vegas, Phoenix and Washington, DC.
Some locations had a brief taste of fall-like weather in the last couple of weeks only to have this summer’s sizzling temperatures reemerge with a vengeance.
Take Philadelphia, for instance. High temperatures in the low to mid-70s made it feel like late-September for a few days last week. But the heat index – how the combination of heat and humidity feels to the body – will hit the triple-digits there on Wednesday.
Tens of millions of people were under heat alerts Wednesday with potentially record-breaking high temperatures possible in the East and widespread highs in the 90s and lows 100s for much of the country.
This temperature rollercoaster could be a theme of the season. Despite continued cool flashes warmth appears poised to stick around in fall for much of the US.
Fall temperatures might not fall much
Fall technically starts in September, but the more consistent cooler temperatures associated with it become more widespread across the country by the second half of the month. The problem is, summerlike heat isn’t going down without a fight, according to the latest forecasts.
The most unusual warmth forecast during the month stretches from the central and southern Rockies southeast through the South and then north up the entire East Coast.
The northern tier of the country from the Pacific Northwest to the Upper Midwest has the greatest chance to remain closer to normal, according to the Climate Prediction Center.
Above-average temperatures will largely continue through October and November, according to the CPC.
The entirety of fall will not feel exactly like summer even with elevated average temperatures. Typical high temperatures drop by around 20 to 25 degrees from mid-July to mid-October for much of the US.
Denver, for example, falls from a normal high near 90 degrees in July to a high in the mid 60s in October.
Hurricanes could lower the thermometer
The East Coast could get somewhat of a reprieve from abnormal warmth this fall if an active hurricane season has anything to say about it.
Despite some quiet periods, the Atlantic hurricane season is expected to pick up again soon. La Niña is expected to build during the fall and could enhance tropical activity in the Atlantic. The natural climate pattern marked by cooler than average ocean temperatures in the tropical Pacific Ocean exerts its greatest influence on US weather in winter, but signs of it could arise later this fall.
Forecasters are monitoring potential tropical trouble at the turn of the month; the climatological peak of hurricane season is less than two weeks away; and the most active portion of the season continues through mid-October.
Any storms that pass near US coasts through the end of hurricane season could also unload rain and “result in periods of cooler-than-normal temperatures for these areas this fall,” the CPC said.
The active hurricane forecast also means the East Coast could end the fall wetter than normal.
The other extreme is possible over large sections of the western and central US, where lower than normal precipitation is forecast. A lack of necessary rain could worsen drought conditions in areas that have already spent the summer drying out.