March Heat Ends for Much of USA

The most unbelievable spring heat wave in North American recorded history is finally drawing to a close today, after a ten-day stretch of unprecedented record-smashing intensity. Since record keeping began in the late 1800s, there have never been so many spring temperature records broken, and by such large margins. 

Airports in fifteen different states have set all-time records for March warmth, which is truly extraordinary considering the records were set in the middle of the month, instead of later in March. The 29.2°C (85° F) measured at Western Head, Nova Scotia yesterday was the third warmest temperature ever recorded in Canada in March, according to Environement Canada (top two records: 31.1° C at Alberini Beaver Creek, BC on March 29th 1926, and 29.4° C in 1921 at Wallaceburg).

Michigan's all-time record for March warmth was toppled on Wednesday, when the mercury hit 90° F (32.2° C)  at Lapeer. The previous record, 89° F at Lapeer in 1910, was matched at three stations yesterday-- Ypsilanti, Dearborn, and Lapeer. The duration, areal size, and intensity of the March heat wave are off-the-scale, and the event ranks as one of North America's most extraordinary weather events in recorded history. 

Clear skies over the eastern USA caused by a blocking ridge of high pressure on March 21, 2012, are highlighted in the visible satellite image above.  The comma-shaped cloud pattern over the Great Plains is associated with a cut-off low pressure system.  The low is slowly moving across the South today and will bring an end to the summer-like temperatures over much of the United States and Canada.  Florida will remain hot and dry as it typical this time of year.

Records Fall by Huge Margins

Breaking daily temperature records by more than 30°F

It is exceptionally rare for a weather station with a 50-plus year period of data to break a daily temperature record by more than 10° F. During the March Heat Wave of 2012, beating daily records by 10° - 20° F was commonplace, and many records were smashed by over 20°. Two stations broke records by more than 30° F, which is truly freakish. Western Head, Nova Scotia hit 29.2° C (85°F), yesterday, breaking their previous record for the date (10.6° C in 1969) by 18.6°C (33° F). Yesterday's high temperature was 24° C (44° F) above average.  Pellston, Michigan in the Northern Lower Peninsula--dubbed "Michigan's Icebox," since it frequently records the coldest temperatures in the state -- hit 85° F on March 21. That temperature broke the previous record for the date (53° F in 2007) by 32°, and was an unheard of 48° F above average.

Breaking Temperature Records 

Nine Consecutive Days or More

It is extremely rare for stations with a 50-plus year's of data to break a daily high temperature record for seven or more days in a row. The longest such streak of consecutive high temperature records at International Falls, Minnesota, was a 5-day period March 3 - 7, 2000. The city has tied or broken their high temperature for the date 10 consecutive days, as of yesterday.

Chicago, Illinois has tied or broken their daily high temperature record the past 9 days in a row. This ties the 9-day streak of record highs set on August 26 - September 3, 1953. Other cites that have set daily high temperature records the past 9 days in a row include Fort Wayne and South Bend, Indiana. Numerous cities have broken high temperature records on 7 consecutive days since the heat wave began, including Gaylord, Pellston, and Traverse City in Michigan.

IMPACTS

of the exceptional March Heat Wave

The warm weather has been a huge benefit to the economy of most states affected -- vastly reducing heating costs, snow removal bills, and resulting in far fewer traffic accidents due to icy roads. 

DAMAGING FREEZE LIKELY

However, there is major downside to the heat wave. The growing season is now in full swing, five weeks early. A damaging freeze that will severely impact the fruit industry and other sensitive plants is very likely. 

The forecast calls for lows in the upper 20°s F (-2° C) in the cherry-growing region of Michigan near Traverse City on Monday night. The exceptional March warmth has also melted all the snow in the northern United States and southern Canada, drying out the soils and setting the stage for a much warmer than average summer, and an increased chance of damaging drought conditions. 

The early loss of snowpack will also likely cause very low flow rates in the major rivers in late summer and early fall, reducing the amount of water needed for irrigation of crops. Low flows may also cause problems for navigation, limiting commercial barge traffic on Midwest rivers.