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Heat Wave Sizzles On, Toppling More Than 2,000 Records

Records continue to fall across much of the U.S., as the extraordinary March heat wave rolls onward. The warm weather, with daytime high temperatures close to 40°F above average in some places, set the stage for severe thunderstorms that spawned rare, damaging March tornadoes near Detroit.

The warm weather is the result of a weather pattern that has become stuck in place, known as a “blocking pattern,” with a stubborn, sprawling area of high pressure in the eastern U.S. that is pumping warm air northward into the Great Plaines, Midwest, Ohio Valley and Northeast. The West, on the other hand, is cool and stormy, with mountain snows and valley rains associated with a big dip or “trough” in the jet stream. As this trough slides slowly east, it may set the stage for an outbreak of tornadoes in the Plains late this weekend, as the cool air collides with the warm and more humid air that lies to the east.

Forecast temperature departures from average for Sunday, March 18. Click on the image for a larger version. Credit: Ryan Maue

During the past week, more than 1,200 temperature records were set. During March so far, more than 2,000 daily record-high temperatures have been set in the U.S., and warm temperature records outpaced cold records by a ratio of about 9-to-1.

On March 15 alone, 593 record daily high temperatures were set or tied, along with 445 record warm low temperatures. This compares to just 10 record cold high temperatures, and only 2 record cold overnight lows. In Chicago, temperatures have soared past 80°F four days in a row — the earliest that has ever occurred, breaking a record set in mid-April, 1896.

The National Weather Service issued a statement saying: "It is extraordinarily rare for climate locations with 100+ year long periods of records to break records day after day after day... though it is very difficult to precisely quantify just how rare it is because as the period of record grows the likelihood of seeing so many consecutive record-breaking days decreases."

In a long-term trend that has been found to be inconsistent with natural variability alone, daily record-high temperatures have recently been outpacing daily record-lows by an average of 2-to-1, and this imbalance is expected to grow as the climate continues to warm. According to a 2009 study, if the climate were not warming, this ratio would be expected to be even. Other studies have shown that climate change increases the odds of extreme heat events.

Jake Crouch, a climate scientist at the National Climatic Data Center in Asheville, N.C., said the heat wave is comparable to severe summer heat events in terms of the number of records that have been broken, even though temperatures aren’t as hot as they would get during a summer heat event.

Temperature forecast for Tuesday, March 20, showing warm temperatures across much of the country. Credit: NOAA/HPC.

“The number of warm maximum temperature records rival the heat waves that have affected the U.S. in the past,” Crouch said, noting that Nevada is the only state in the lower 48 that has not set a daily high temperature record this month.

The warm weather provided the fuel for severe thunderstorms in Michigan, with multiple tornado touchdowns reported near Detroit. One tornado that touched down in Dexter, Michigan was rated an EF-3 on the Enhanced Fujita Scale. It demolished homes, but fortunately did not result in any fatalities. 

As noted by WeatherUnderground’s Jeff Masters, this was the earliest that such a powerful tornado had occurred in the state since reliable records began in 1950.

The National Weather Service released a statement saying that Chicago and Rockford are on pace to "not only break... but shatter" their records for the warmest March.

Here are some of the noteworthy records set on March 15-17. 

  • Minneapolis: 79°F on March 16, the warmest it's ever been s early in the year, and 39°F above average.
  • Rockford, Ill.: 82°F on March 15, breaking the old record of 73°F set in 1995. This was the earliest 80-degree reading on record for this location. Rockford set another daily record on the 16th with a high of 80°F, and on the 17th, with a high temperature of 82°F.
  • Chicago: 81°F on March 15, breaking the old record of 74°F set in 1995. Chicago has been running nearly 12 degrees above average for the first half of March. On March 16 and 17, Chicago hit 82°F, which was the earliest it had ever been that warm. The previous record was set on March 27, 1945, and 82°F is the typical record high for June 24, the National Weather Service reported.
  • Bismarck, N.D.: 81°F on March 16, the warmest all-time March temperature on record. (H/T Jeff Masters.)
  • Madison, Wisc.: 82°F on March 15, breaking the old record by 13 degrees, tying the record for the warmest temperature on record during the month of March, and setting the record for the earliest 80-degree day, beating the old date by nearly two weeks.
  • Williston, N.D.: 68°F on March 15, beating the old record of 67°F set in 1996.
  • Minot, N.D.: 64°F on March 15, exceeding the old record of 62°F set in 1938.
  • International Falls, Minn.: 71°F on March 16, which was their earliest 70°F reading. The temperature reached 77°F on March 17, which set an all-time monthly record, beating the old monthly record by 4°F.
  • Moline, Ill.: 81°F on March 15, the warmest it's ever been there so early in the year. This broke the previous record of 80°F on March 12, 1990.
  • Dubuque, Iowa: 78°F on March 15 and 16, the warmest it's ever been there so early in the year, going back to 1874. This record was short-lived, however, since it was toppled on March 17, when the temperature reached 81°F
  • Cedar Rapids, Iowa: 75°F on March 15, 79°F on March 16, and 82°F on March 17, which was the earliest 80-degree reading on record.

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