Published: August 18,2017
A similar pattern to this summer's conditions may persist into fall, according to the latest outlook from The Weather Company, an IBM Business.
The West is expected to see near- to slightly above-average temperatures this fall, defined as the September through November period. One exception is the Southwest, where overall above-average conditions are expected.
(MORE: Signs of Fall That Can Appear in August)
Meanwhile, the Midwest, as well as much of the Mississippi Valley and Northeast, are more likely to experience near to slightly cooler-than-average temperatures. This excludes most of the South and parts of the Northeast, including southern New England, where temperatures are more likely to be near to slightly warmer than average.
Fall 2017 temperature outlook from The Weather Company, an IBM Business.There are indications that the months-long dominant upper-level pattern will influence temperatures into September.
Dr. Todd Crawford, chief meteorologist with The Weather Company, said computer forecast models have been "pretty persistent about producing a pattern similar to that seen in the first half of August."
That pattern has featured far-below-average temperatures for many locations east of the Rockies and temperatures well above average in the Pacific Northwest.
In addition, El Niño conditions are no longer anticipated to develop this fall or winter; the most recent outlook from NOAA said ENSO-neutral conditions are expected.
"Cooler changes have been made to the fall forecast given the expected continuation of the August cool pattern into September and a notable shift back towards La Niña conditions in the observations and model forecasts over the past month that would argue for a cooler early start to the heating season," said Crawford.
(MORE: The Most Notorious Portion of the Atlantic Hurricane Season Has Arrived)
An important note: tropical activity can impact the weather pattern across the U.S. in September and October, which would alter the current temperature forecasts.
SeptemberThe upper-level pattern consisting of a ridge of high pressure, or northward bulge of the jet stream, over the West and a trough, or southward dip in the jet stream, over parts of the East is expected to prevail into September.
(MAPS: Weekly Planner and 30- and 90-Day Outlooks)
This pattern is expected to bring cooler-than-average temperatures to start the fall in portions of the central and southern Plains, as well as the mid-Mississippi Valley.
Parts of the Midwest, South and mid-Atlantic will likely see temperatures near or slightly cooler than average. However, parts of the Northeast and most of Florida may see conditions that are near or slightly warmer than average.
Meanwhile, this pattern would also result in above-average temperatures from California into the Northwest.
September 2017 temperature outlook from The Weather Company, an IBM Business.
OctoberMuch of the U.S. will see temperatures near or slightly above average in October.
The exception will be from the Southwest into parts of the southern Plains, where temperatures will generally be warmer than average.
(MAPS: Average Monthly Temperatures)
In addition, parts of Florida, northern New England and the Upper Peninsula of Michigan into northeastern North Dakota are more likely to see near to slightly cooler-than-average conditions.
October 2017 temperature outlook from The Weather Company, an IBM Business.
NovemberCloser to winter, the Southwest will once again be the area expected to see above-average temperatures.
A large swath of the U.S., stretching from the Northwest into the Plains and Southeast can expect temperatures to be near or slightly above average.
(MORE: What Does a Lack of El Niño, La Niña Mean For Winter?)
Much of the Midwest and Northeast, however, will likely see temperatures near or slightly below average.
November 2017 temperature outlook from The Weather Company, an IBM Business.
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.