Cities Across U.S. Bore Brunt of Record-Setting July Heat

Preliminary climate data for July shows that many cities across the U.S. experienced record-setting months, with temperatures propelled upwards by a massive area of High Pressure, more popularly known as a Heat Dome, that kept cooling rains at bay.

For example, in St. Louis, Mo., where the year-to-date has been the warmest such period on record, the city has already exceeded its all-time record for the greatest number of days with high temperatures of 105°F or above, beating the 10 such days that occurred during the Dust Bowl in 1934.

Triple-digit heat affected all of Oklahoma on July 31. Click on the image for a larger version. Credit: Oklahoma Mesonet.

In Wichita, Kan., July was the fourth warmest month on record, tied with 1934. Wichita recorded 21 100-degree days during the month, which was the second greatest such tally ever recorded there during the month of July.

July was also Denver’s warmest month on record, with an average temperature of 78.9°F, beating the previous record that was set in 1934 by more than a full degree. The “Mile High City” had seven 100-degree days, and there were 27 days with a high temperature of 90°F or higher.

And for many in the lower 48 states, August is coming in the same way July ended — dangerously hot, with only sporadic rain showers. In Oklahoma City, high temperatures on Wednesday were forecast to “flirt with” the city’s all-time high temperature record of 113°F, according to the National Weather Service (NWS). Tulsa, Okla., is likely to come close to its all-time record of 115°F as well.

Of all the areas that have been hammered by the intense heat, the Mississippi Ozarks and southeast Kansas may take the prize for enduring the worst of it, at least during the past two weeks, when a brutal combination of high heat and a pronounced lack of rainfall took hold. In Joplin, Mo., the average high temperature during July was 99.7°F, and the city only received a trace of rainfall. Joplin’s average temperature during July was 6.4°F above average, and the month ranked as the city’s fourth-warmest on record.

July's heat also extended northward to Chicago, where the “Windy City” experienced its third-warmest July, with an average temperature of 81.1°F, which was 7.1°F above normal. In Rockford, Ill., July was the warmest such month on record, with an average temperature that was 7.0°F above average.

In Oklahoma City, high temperatures in 2012 (red line) have been well above average. Large grey background is the all-time temperature range. Dashed lines are 15 day running mean temperature, and the small grey box shows daily norms. Click on the image for a larger version. Credit: Patrick Marsh.

On the East Coast, Washington D.C. had its second-hottest July, exceeded only by July 2011, which was 0.5°F warmer. This July, however, set new standards for the greatest number of 100-degree days, with seven, and tied 1930 for the longest string of consecutive 100-degree days, with four. According to the Weather Service, one-third of July days now have record high-minimum temperatures that were set in either 2010, 2011, or 2012, indicating that each of the past three Julys have featured unusually warm overnight low temperatures.

The record warm July comes in a year that has been extraordinarily warm, particularly in the U.S., where record daily high temperatures have been outnumbering record daily low temperatures by a nearly 9-to-1 ratio. As of June, the latest month for which figures are available, we've experienced the 328th month in a row — that's more than 27 years — with global temperatures above the 20th century average. The last month to come in below average was February of 1985.

For the U.S., the warm July follows a warmer-than-average June, which came on the heels of the warmest spring on record, which in turn was the culmination of the warmest March, third-warmest April, and second-warmest May. This year marked the first time that all three months during the spring season ranked among the 10 warmest, since records began in 1895. The heat has been accompanied by, and is also feeding off of, an expanding and intense drought, which is now covering a majority of the country.