Exceptional heat wave topples October records across much of the U.S.

It’s another steamy summer day across the eastern half of the United States. The only problem? It’s October.

Temperatures are peaking on Wednesday during an extended stretch of high heat and humidity east of the Mississippi River. The mercury is soaring well into the 90s from the nation’s capital to Florida to Texas, and just about everywhere in between. Wednesday looks to be the hottest day before the heat settles south of Interstate 20 by Friday and into the weekend.

As of 2:08 p.m., the District of Columbia had broken its all-time monthly high temperature record with a temperature of 98 degrees, easily beating the old record of 96 degrees set on Oct. 5, 1941.

The high in Newark hit 94 — 24 degrees above normal — while the temperature in New York’s Central Park reached 92 degrees for the first 90-degree or higher reading in October since 1941.

It’s no different elsewhere up and down the Mid-Atlantic. Baltimore reached 98 degrees Wednesday, which easily became its hottest October day on record. Wilmington, Delaware hit 96 degrees so far — both a record for the date and the month. Previously, they had never climbed above 91 in October. It’s a similar story in Atlantic City, New Jersey, where the previous October record high was 90 degrees. It has climbed to 95.

Philadelphia, meanwhile, broke into the 90s as well. By Thursday, however, the city will see temperatures fall dramatically, with highs stuck in the lower to mid-60s as a cold front sweeps in with northeasterly winds and occasional rain.

To the south, Greer, South Carolina shattered its former monthly record high by 5 degrees. Fulton County Airport in Atlanta did it by 4 degrees, breaking a record they set just last year; that record had broken one from 2016.

In all, about 209 million people, or about 71 percent of the population of the Lower 48, were forecast to see high temperatures of at least 80 degrees on Wednesday, with 131 million seeing temperatures at or above 90. These are remarkably high numbers for Oct. 2.

The heat on Wednesday follows a historically steamy Tuesday, when more than two-dozen high temperature records were broken for the date in the eastern United States, along with 16 locations that set their highest temperature for any October day, according to the National Weather Service.

Farther south, that heat is in no hurry to leave.

Take Atlanta, for instance. Hartsfield-Jackson International Airport has never recorded a temperature above 95 degrees this late in the year, but the National Weather Service is predicting a 96-degree high on Wednesday, Thursday and Friday. Temperatures will finally “cool” into the 80s for the weekend, yet they will still run several degrees above average through next week.

It’s been a remarkable summer and early fall for extreme heat in Atlanta and the rest of the Southeast. The city hit 90 degrees an astonishing 23 times in September — surprising when you consider the average September high is between 78 and 86 degrees. September as a whole wound up a hair under nine degrees above normal.

Atlanta has not seen a high below average since Aug. 26.

Birmingham, Ala., meanwhile could hit 100 degrees on Wednesday, something that has never happened there after Sept. 22.

On Tuesday, Birmingham logged a 99 degree reading — beating the previous October all-time high record by five degrees, which is an extreme margin.

The cause of the heat wave is a large area of high pressure anchored over the Southeast, which is pumping warm and relatively humid air northward, while squelching rainfall and keeping relief-providing cold fronts at bay.

The heat dome stretches back into Texas, where the 90s will stick around into the weekend. 

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While the heat wave peaks across much of the central and eastern states, in the Northern Rockies, winter has arrived early, with several feet of snow falling in Montana over the weekend, and with a small number of locations experiencing record lows in the wake of that storm. The temperature fell to a mere 9 degrees in Great Falls, Mont., on Oct. 1, obliterating the previous low of 22 degrees from 1959.

However, nationwide, the high temperature records overwhelmingly outnumber the cold records during the past week as well as longer periods as well. This is consistent with trends that have been tied to human-caused global warming, which is favoring warm temperature records, particularly above average overnight low temperatures.