A Warm Spin on Late November Across Much of U.S.

Record heat slathered the U.S. Southwest like holiday gravy throughout the Thanksgiving weekend, and the late-November warm wave began spilling into the central states on Monday. Before the week is done, at least a few U.S. locations are likely to end up with their warmest November on record.

The holiday heat got off to an early start in southern California: Anaheim hit an exceptional 100°F on Wednesday, the nation’s highest temperature of the day. By early Monday, the warm air was pushing across the Great Basin and onto the High Plains, courtesy of strong west winds rotating around a storm system centered far to the north, in Saskatchewan. As noted by weather.com’s Linda Lam, Salt Lake City set a daily high temperature record just after 2 AM MST Monday with a balmy 68°F, one day after a record high of 69°F on Sunday. Temperatures vaulted into the mid-70s on Monday morning in Boulder, Colorado, a few miles away from the Eldora ski area, which opened for the season on a mild, snow-free holiday weekend.

Dozens of record highs are likely to tumble on Monday across the southern and central Great Plains. At 11 AM MST, it was already 76°F in Goodland, KS; 78°F in Sidney, NE; and 81°F in La Junta, CO—all records for the date.

For the week ending Saturday, the NOAA/NCEI U.S. Records site tallied a preliminary total of 830 daily record highs and 1075 record-high daily minima, compared to 11 daily record lows and 29 record-cold daily maxima.

Figure 1.  Most sites across the Southwest U.S. were experiencing a top-ten warmest November as of Sunday, Nov. 26. The numbers at each site show how the month ranks thus far compared to all Novembers observed at that site, with “1” denoting the warmest November on record. Image credit: Southeast Regional Climate Center.

Toasty times in Tucson

Among the locations where heat records for so late in the year were toppled over the weekend were San Jose, CA (80°F on Saturday), Cheyenne, WY (71°F on Sunday—the latest 70°F on record in data going back to 1872), and Casper, WY (67°F on Sunday). Tucson, AZ, had its hottest day so late in the season with 88°F on Saturday, and then bested itself with 92°F on Sunday. The Sunday reading in Tucson was just 2°F shy of the city’s all-time November record—an especially impressive feat given that we’re near the end of an autumn month, when the mildest readings typically arrive sooner rather than later. Tucson notched daily record highs on all four days of the holiday weekend (Thurs-Sun), and it’s racked up a total 21 record highs for the year thus far. “With a period of record starting in 1894, having almost 7% of all days this year attaining record warmth is quite unusual,” said WU weather historian Christopher Burt.

More than 20 sites across the Southwest experienced their warmest Nov 1-26 period on record, as shown in Figure 1 above. Temperatures will be dropping from their record perch this week across the Southwest, but at least some of these stations are still likely to end up with their all-time warmest November. Although the month has been slightly cooler than average from the far northern Plains across the Midwest to the Northeast, it’s hardly been the wintry onslaught that some extended models were suggesting at the start of the month.

Figure 2.  Departures from average temperature for the period Nov. 1-25, 2017. Image credit: NOAA/NWS Weather Prediction Center.

Wrapping up a 36th consecutive month of more heat than cold records

November appears to be a lock for ending up with more U.S. daily record highs than lows. This brings us to a noteworthy point, according to climatologist Guy Walton: November will be the 36th month in a row where U.S. daily record highs outnumbered record lows. In his exhaustive month-by-month calculations of U.S. records dating back to 1920, Walton shows that no other 36-month period has been such a consistent producer of either heat or cold records. On Sunday, he called the 36-month milestone “a landmark for my personal climate change marker.”