Regional Forecasts

Why October Won't Finish Like It Started

At a Glance

The first half of October saw near-record warmth in much of the East.
The weather pattern began to change in mid-October across the U.S.
Cool temperatures are likely in parts of the central, eastern U.S. into late October.
Snow is possible in parts of the interior Northeast.

Warmer-than-average temperatures were the norm for much of the first half of October in the eastern United States, but the second half of the month will see the polar opposite, with frequent intrusions of cold air.

This dramatic change is due to shifts in the upper-level weather pattern across the U.S.

The jet stream pattern in early October featured an upper-level ridge of high pressure over the East, with a southward plunge over parts of the western and central U.S.

Shifts in the upper-level pattern began to take shape in mid-October as the upper-level trough, or southward dip in the jet stream, slid eastward.

Setup for cooler-than-average temperatures in the eastern U.S. into late October.

This southward dip in the jet stream has allowed colder-than-average conditions to surge southward over parts of the central and eastern U.S., and this upper-level pattern will likely generally remain over the East into the end of October.

(MORE: 4 Extreme Weather Events We Witnessed in October’s First Half)

Temperature Changes

The upper-level pattern in early October allowed well above-average temperatures to dominate locations from the Northeast to the Gulf Coast while areas from the northern Rockies to the upper Midwest saw well below-average conditions.

Through Oct. 14, many sites saw one of the warmest October-to-date on record, according to the Southeast Regional Climate Center. This includes Washington D.C., which saw its warmest first half of October on record, with an average temperature of 71.8 degrees. The warmest start to October was also recorded in Allentown, Pennsylvania; Atlantic City, New Jersey; Charleston, South Carolina; New Orleans and Brownsville, Texas.

Atlanta experienced its second-warmest first 14 days of October, with an average temperature more than 9 degrees above average. Cleveland saw its third-warmest such period, with the average temperature 8 degrees warmer than average.

Average temperatures from Oct. 1 through Oct. 14. Red and orange boxes indicate well above-average temperatures while blue and purple boxes denote colder-than-average temperatures.
(Southeast Regional Climate Center)

There have been recent cooldowns across the East and South, and some of the higher elevations of the Northeast even saw their first snow of the season last weekend. There have even been many daily record-cold temperatures in the Plains and Midwest while parts of the Southeast have seen daily record highs.

Another reinforcing cold front is pushing east and southward, bringing another shot of colder temperatures this weekend. This frontal system will push farther south than recent systems, even through South Florida.

Temperatures will drop to 5 to 20 degrees below average for this time of year behind this weekend's cold front.

Light snow is likely south and east of the eastern Great Lakes and in the northern Appalachians on Sunday and east of Lake Ontario into Monday.

Highs late this weekend and into early next week will only top out in the 40s in parts of the Northeast, with 50s toward the coast and in the mid-Atlantic. Widespread highs in the 50s, 60s and 70s are expected across the South, with low- to mid-80s in central and southern Florida.

The coldest temperatures of the season are likely early next week for much of the East.

By Sunday or Monday morning, low temperatures will plunge into the 30s as far south as northern Mississippi, northern Alabama, Tennessee, north Georgia and portions of South Carolina and North Carolina, with 40s and 50s for much of the South.

Forecast Lows
(Contour on the map is forecast lows for Monday morning.)

This cold blast will likely bring the first frost and freeze of the season for many locations.

(MORE: When Your First Freeze Typically Arrives)

Another reinforcing shot of cold air could sweep through the Great Lakes and Northeast by Tuesday or Wednesday.

How Long Will The Chilly Conditions Last?

There are indications that the overall colder-than-average temperature trend in the East and at least parts of the central U.S. will persist through the end of October and potentially into November.

The highest chance for chilly conditions will be along the East Coast and in the Appalachians.

This is shown by the latest 6- to 10-day temperature outlook from NOAA's Climate Prediction Center. This outlook also shows that Florida may continue to see overall warmer temperatures.

The West into the northern Plains also has an increased chance of experiencing warmer temperatures in late October. This would be a notable change in the Rockies and northern Plains, where many areas have seen one of the coldest first half of October on record.

There are indications that temperatures may moderate in the East to begin November, but the over "cold east, warm west" pattern should continue.