SIOUX FALLS, S.D. (KELO.com) — The dog days of summer are still ongoing with heat waves across the country and mild and muggy summer nights, but a shift in the weather is right around the corner as the Northern Hemisphere heads toward the fall season.
Autumn, which will officially begin with the autumn equinox on Sept. 22, 2021, features more than just a change in the weather. The new season brings about a flurry of fall festivals, the return of football and the ever-popular leaf-peeping, when folks flock to forests to see trees transform into a vibrant tapestry of color.
Anyone planning to partake in the variety of outdoor fall activities should be sure to check the AccuWeather app first as Mother Nature can turn a trip to a pumpkin patch into a damp and drizzly outing. Knowing the overall weather patterns expected in the upcoming season can help when making plans, and AccuWeather has you covered.
A tractor tows a trailer full of visitors past a pumpkin patch during a visit to a fall festival at an orchard and farm market in Wexford, Pa., Saturday, Oct. 4, 2014. (AP Photo/Keith Srakocic)
AccuWeather’s team of long-range forecasters has been analyzing the ongoing weather patterns, various computer models and looking back at past years to formulate a seasonal outlook — providing insights into the anticipated trends in September, October and November.
Veteran forecaster and senior meteorologist Paul Pastelok leads the team and has helped to break down exactly what folks can expect, ranging from the first frost in the Northeast and Midwest, the peak of the Atlantic hurricane season and the widespread drought and wildfire concern across most of the West.
AccuWeather Senior Meteorologist Paul Pastelok breaking down the fall outlook for the U.S.
One of the bigger factors that will influence the country as a whole this autumn is becoming a more familiar term: La Niña.
La Niña is a climate phenomenon that occurs when the waters near the equator of the Pacific Ocean are cooler than normal. It alters weather patterns thousands of miles away, including across the United States, and this is the second autumn in a row that La Niña has played a role in the seasonal outlook.
Not only is a La Niña expected to develop, but it may also do so early on in the season for the second year in a row, Pastelok said, adding that may spell bad news for some.
“Typically, we usually see La Niña come on about late fall to the winter season on average, but this year, it looks like it’s going to come in early just like it did last year,” Pastelok said.
The return of La Niña is signaling yet another above-average hurricane season, as well as some other high-impact weather events across the contiguous U.S. in the coming months.
Whether you’re ready to break out your fall decorations or you’re relishing in the last weeks of hot, sunny weather, read on below to see what conditions are headed your way in the coming months with the region-by-region breakdown of the autumn forecast.
Warmth to linger in Northeast, Midwest
Meteorological autumn kicks off on Wednesday, Sept. 1, but it may take some time for the fall-like weather to arrive for residents from Boston through Chicago.
“It seems like every year we’re dealing with that as the kids go back to school, it seems like we get a warm spell,” Pastelok said.
This year is no exception to that notion with above-average temperatures in the forecast for New England, the mid-Atlantic and westward through the Midwest.
Some spells of rain and stronger thunderstorms will be possible in September and early October amid the warmer-than-normal weather, a continuation of the storms that rumbled over the regions during the late summer. There could also be some bouts of rain associated with tropical systems.
The warmth is forecast to continue through September and into early October and could affect more than outdoor plans. Spells of warmer-than-normal weather can sometimes delay the onset of the fall foliage, but the wait may be worth it this year.
Early indications are pointing to trees being pretty healthy across this part of the country, Pastelok said. “The foliage may turn out to be pretty good this year … as long as we don’t see any prolonged dry conditions,” he explained.
A road twisting through a colorful wooded area near Long Pond, Pennsylvania, during autumn. (Image/ Craig Adderley)
Partway through October, the pattern will start to flip, ushering in some of the coolest air the Midwest and Northeast have experienced since the spring.
“The best chance of seeing some early cold is not until late October or November,” Pastelok said.
In terms of the first frost of the season, the window of late October to early November is right around the normal date for many areas, although some spots of northern New England and upstate New York could see frost by mid-October. And depending on what exactly unfolds, some spots could see more than just frost.
Pastelok explained that this late-October flip in the pattern will bring the first chance for early-season snowfall. The Great Lakes and upstate New York will face the highest chances for some early-season snowflakes.
This will be followed up by more frequent intrusions of colder air through November which could cause the lake-effect snow machine to begin to churn out fresh powder downwind of the Great Lakes.
According to AccuWeather’s Senior Vice President of Forecast Operations Jonathan Porter, November will also bring the risk for an early accumulating snowstorm.
“A stronger, northern storm track caused by the return of La Niña may send an early clipper-style storm or two across the Midwest and Northeast,” Porter said.
Tropics to remain active, but shift focus in 2021
The 2020 Atlantic hurricane season rewrote the record books, and yet another busy season is expected. To make matters worse, some residents are still struggling to get back to normal after being bombarded by a string of weather disasters that started back with Hurricane Laura, which crashed onshore as a Category 4 hurricane, packing 150-mph winds, near Cameron, Louisiana, in late August 2020.
The 2021 season wasted no time getting started with Subtropical Storm Ana taking shape on May 22, eventually being upgraded to tropical storm status. Tropical Storm Claudette became the first tropical system to make landfall in the U.S. this season on June 19, followed up by Hurricane Elsa that hit on July 5.
Danny Gonzales, right, stands in front of his flooded house with his neighbor Bob Neal, upset with power company trucks driving through the flooded neighborhood pushing water back into his home, after Tropical Storm Claudette passed through, in Slidell, La., Saturday, June 19, 2021. (AP Photo/Gerald Herbert)
Pastelok warned that La Niña will play a factor in the tropical season, and it is one of the reasons why another above-normal season is in the forecast.
More storms could develop through the course of the season due to the pattern limiting a factor called vertical shear mechanism. With less interruptive winds in place, tropical storms and hurricanes can more easily become better organized — as opposed to during an El Niño year when winds can keep systems in check.
AccuWeather forecasters are predicting a total of 16-20 named storms, which includes 7-10 hurricanes. This is more than the seasonal average of 14.4 named storms and 7.2 hurricanes, an average that has increased in recent years. Additionally, five to seven storms are projected to make landfall in the U.S.
Although La Niña will influence hurricanes for the second season in a row, there will be some differences when compared to the 2020 season.
Last year, storms focused on the Gulf Coast from eastern Texas to the Florida Panhandle with multiple high-impact storms slamming into Louisiana.
This year, more storms could turn up and swipe the Atlantic coast all the way from Florida to southern New England, or take a more westerly track and head toward Texas. However, a landfall in Louisiana, Mississippi or Alabama cannot be completely ruled out.
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Pastelok explained that cold fronts swinging across the eastern U.S. will be the influencing factor that will cause tropical systems to take the turn up the Atlantic coast rather than head toward the central Gulf Coast.
Whether or not storms will hug the coast or swing well east of the coast is difficult to pinpoint at this point, Pastelok explained, but residents of the East Coast shouldn’t let their guard down. The East Coast, anywhere from Florida to southern New England, could be vulnerable.
These cold front could also set off strong thunderstorms across part of the Plains and into the Mississippi, Tennessee and Ohio valleys.
The number of tornadoes that have touched down across the country has been below normal to date, and even with autumn bringing a secondary peak in severe weather, the annual tornado count is likely to stay below normal.
As of Sunday, Aug. 1, only 828 tornadoes have been reported, well below the 1,108 twisters that are usually tallied by the start of the month, according to data from the Storm Prediction Center.
“I do feel that we will fall short of the normal amount of tornadoes,” Pastelok said. He added that there could be an uptick in tornado-producing storms in late October and November from the central Gulf Coast to the southern shores of the Great Lakes, but even so, the year as a whole is likely to finish with fewer tornadoes than normal.
Big changes coming for Plains, Rockies mid-Autumn
It has been a hot and dry summer for most of the northern Plains and across the Rockies, and more of the same is on tap to start autumn before big changes arrive.
“We’ve seen a lot of cold air built up in northern Canada already,” Pastelok said, “but I do feel like the setup getting into October could be ripe for the northern Rockies.”
This flip of the switch in October will send the first waves of cold air pouring into the central U.S. to provide relief from the prolonged heat. The weather may go straight from summer — with heat and wildfires — to an early preview of winter during October.
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This shift in the pattern will also bring some much-needed drought relief to the northern Plains with pockets of extreme to exceptional drought across portions of Minnesota, the Dakotas and Montana, according to the U.S. Drought Monitor.
However, this delay in the onset of autumn precipitation will be beneficial to farmers.
“We do feel like it looks favorable for the harvest across western sections of the Corn Belt, Minnesota, Dakotas, parts of western Iowa, because of the fact that we’re not looking at a lot of systems to get in during the time of harvest,” Pastelok said.
Farther south, the midseason shift in the weather pattern will be welcome for snow-lovers waiting to hit the slopes for the first time since spring.
In this Wednesday, May 27, 2020, file photograph, 6-year-old Nara, left, and 5-year-old Hana Davis of Denver prepare to hit the slopes at the reopening of Arapahoe Basin Ski Resort. (AP Photo/David Zalubowski, File)
“The skiers are waiting for this forecast to bring on the snow,” Pastelok said, adding that “mid-fall is probably the best shot.”
However, Pastelok warned that this will not open the floodgates for snow in the Rockies.
October is looking like a month for snow in the mountains from Idaho and Montana all the way down into Colorado, allowing some resorts to open on time despite current drought conditions, but the snow may let up come November.
Snowfall will wane “a little bit” late in the season, but that won’t dictate the entire snow season. Snow is predicted to come back again in the winter, Pastelok said.
A solid early-season snow base is not just beneficial for resorts and skiers, but also in the longer range when mountain snowmelt next spring and summer will feed streams and rivers that have been running below normal due to the drought.
Water reservoirs, such as Lake Mead, depend on rain and snowmelt for both recreation and hydroelectric power. With Lake Mead water levels at historically low levels, a bountiful winter is needed to help water levels rebound a bit following years of gradual decline.
Drought to fuel historic wildfire season in western US
The record books may be rewritten at the end of the year with one of the five worst fire seasons on record in the forecast for the western U.S.
The Bootleg Fire in southern Oregon, which ignited on July 6, is already one of the largest in the state’s history and has burned over 413,000 acres, and the wildfire season is just getting started.
“Autumn doesn’t look good,” Pastelok said. “The wildfire season is going to be nasty all the way through the fall season and possibly into early winter.”
A firefighting crew from New Mexico rests after mopping up spot fires near the Northwest edge of the Bootleg Fire on Friday, July 23, 2021, near Paisley, Ore. (AP Photo/Nathan Howard)
Moisture from the North American monsoon — which has been the most robust since 2015 — has helped to dampen the wildfire threat across the Four Corners region and even helped put a small dent in the ongoing drought, but that wasn’t the case in California and Oregon where the worst of the fire conditions are expected.
“We’re forecasting a top-five year based on the pace, the fuels, the upper pattern and the drought situation, all of that was factored in our forecast,” Pastelok explained.
AccuWeather’s long-range meteorologists are predicting 9.5-million acres to be burned across the western U.S. during the wildfire season, which may not end until December for some areas.
The effects of the wildfires will be far-reaching well beyond the perimeter of the flames. “There will once again be concerns about reduced air quality from all the smoke,” Porter said.
Smoke can be hazardous to your health, especially those with underlying respiratory problems, such as asthma or COPD.
Northern California and southern Oregon in particular are at a high risk for significant wildfires. And once blazes are raging, they may be difficult to contain or extinguish due to the widespread drought and lack of meaningful rain.
Some storms may start to hit the Pacific coast with beneficial rain and high-elevation snow by the start of October, which is around normal, but the storm track will focus more on British Columbia and Washington and widely miss Oregon and Northern California.
“With drought conditions holding on for over 80% of the West, there’s really nothing [expected] to calm the wildfire season down at this point,” Pastelok said.
Southern California could also experience some major fires, particularly in October and into the first half of November when the highest chance for Santa Ana Wind events will occur. These down-sloping wind events can fan the flames of wildfires, causing them to spread rapidly and making them difficult for firefighters to get under control.
The impacts of wildfires will continue to be felt through the winter months even after the flames are extinguished.
Swaths of scarred land, especially in the mountains, will be susceptible to mudslides and debris flows when winter storms finally arrive at the end of 2021 and into 2022. This could bring a second threat to communities near the sites of wildfires for years before enough vegetation can grow back and help keep the ground in place when it rains.
( AccuWeather meteorologist and staff writer, contributed this report.)
