Heat Wave Peaks After Breaking Thousands of Records

By Andrew Freedman

The June to July heat wave finally began to ebb on Saturday, but not before breaking thousands of warm temperature records across the country. In many cases, records that had stood since the Dust Bowl era of the 1930s have been equaled or exceeded, and this event is likely to go down in history as one of America's worst  early summer heat waves.

It is also shining a spotlight on the role that human activities may be playing in this event, since studies have shown that manmade global warming increases the odds of extreme heat events and may make them warmer and longer lasting.

Surface temperatures on Saturday afternoon, July 7. Credit: UCAR.

On Saturday, high temperatures in the triple-digits could still be found in cities such as Baltimore, Charlotte, Cincinnati, Detroit, Philadelphia, Raleigh, and Washington, D.C., among others. However, cooler conditions were moving, or forecast to move, into those areas.

As of 4 p.m,, Washington Reagan National Airport had peaked at 104°F, which broke the daily record, but was 2 degrees shy of that location’s all-time record of 106°F.

The dangerous heat has already begun to lose its grip on parts of the Midwest, but not before shattering all-time high temperature records and causing several heat-related deaths. In Chicago, O’Hare Airport hit 103°F on Friday, 2 degrees shy of its all-time high, while Midway Airport reached 105°F. The string of three consecutive days of 100°F or higher temperatures (102°F on Wednesday, and 103°F on Thursday and Friday) is just one of three such strings in Chicago’s history, dating back to 1871.

According to the WGN TV weather blog, the period from July 1-7 had an average temperature of 87.4°F in Chicago, which is 13.8°F above normal.

Indianapolis hit 105 °F on Friday, while Cincinnati reached 104°F and St. Louis a remarkable 106°F.

On Friday, relief could not be found farther north, either. Lansing, Mich., had a high of 103°F, which was its all-time highest temperature. Lansing’s weather records date back to 1863. Also on Friday, Grand Rapids hit 104°F, which was its third-highest temperature ever recorded. According to the National Weather Service, Muskegon and Holland, Mich., both tied their all-time record highs as well.

Across the Lower 48 states on Friday, 322 daily record high temperatures were set or tied, along with 192 records for the warmest overnight low temperature. Of these records, 22 were all-time records.

During the period from July 1-6, 1,916 daily record high temperatures were set or tied, along with 1,034 records for warmest overnight lows. And since June 7, which is about when the heat first began to build in the West and the High Plains, there have been an astounding 7,693 warm temperature records set or tied in the U.S. These numbers are likely to increase as more information comes in to the National Climatic Data Center in Asheville, N.C.

For the year, warm temperature records have been outpacing cold temperature records by a ratio of 7-to-1. In a long-term trend that demonstrates the effects of a warming climate, 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.