From the Midwest to the northeastern United States, the first week of fall has not only produced higher temperatures than those seen during astronomical summer, but also some of the latest 90-degree Fahrenheit temperatures on record in many locations.
A large, sprawling area of high pressure centered over the Great Lakes and Ohio Valley has been the culprit of the unusual heat and humidity.
A high pressure system is a clockwise flow of sinking air that can produce long periods of hot and dry weather.
In many locations, record highs that have stood since the late 1800s and early 1900s have been shattered this past week. More record highs are forecast to fall on Tuesday.
Before temperatures are trimmed late this week, Pittsburgh is expected to record 12 consecutive days of highs in the 80s. The previous longest stretch so far this year was the 10 days spanning late June to early July. On Sunday, Pittsburgh reached 90 F for the first time since June 13.
New York City recorded its first 90-degree day since Aug. 1 on Sunday.
As of Sept. 25, temperatures in Traverse City, Michigan, reached or exceeded 93 F for four straight days. Previously, Sept. 23 had been the latest 90-degree day on record in Traverse City, so that record was broken for two consecutive days.
Traverse City and Chicago are not the only locations to see temperatures this high this late in the year.
Niagara Falls, New York; Cleveland; Burlington, Vermont; and Madison, Wisconsin, have all experienced the highest temperatures on record for this late in the year.
Cleveland reached 94 F on Sept. 25 and set new record highs for five consecutive days dating to Sept. 21. 90-degree heat is expected again on Tuesday, making this the longest stretch of such heat this year.
Record highs were smashed in Burlington, Vermont, on Sept. 24 and 25 when the mercury topped out at 91 and 92 F, respectively. Previously, the latest Burlington had exceeded 90 degrees was on Sept. 16, 1939.
"Syracuse failed to reached the 90-degree mark once in July or August, but reached the milestone on Sept. 25," Deger added.