It's been hot, but ground temperatures can be much hotter

The unrelenting heat across the southern U.S. and other parts of the world continues to break records. Since June 30, Phoenix, Ariz., has been sweltering with temperatures at or above 110 degrees. For what will likely be 25 days in a row, including Monday, this new record smashes the old one set back in 1974 from June 12-29. Based on the current forecasts, Phoenix is likely to stay above 110 degrees during the daytime hours through at least the end of this week. It’s even hot at night with overnight lows in the lower 90s.

The massive heatwave in southern Europe that I wrote about last week is expected to continue this week as well. Officials in Italy named this extensive heat phenomenon “Charon,” which has contributed to many wildfires. Local residents have been forced from their homes in Greece and have led to all-time temperature records being broken across southwestern Europe. Last Tuesday, Rome, Italy, soared to 108 degrees while Sicily baked at 115 degrees. The northern portions of Europe have so far been spared from the intense heat.

Asia has also been suffering from the relentless heat. On July 17, according to China Weather Net, there was a weather station in Sanbao Township, Turpan, Xinjiang Uyghur Autonomous Region in northwestern China that had a high of 126 degrees. That is the highest temperature ever reported in that country. The old record was 123 degrees set back in July of 2017.

Across the Inland Northwest, afternoon temperatures soared well into the 90s last week. The hottest day of the summer season thus far was Friday with a high of 98 degrees at Cliff’s station in northwestern Coeur d’Alene. At the Spokane International Airport, the high temperature Friday topped out at 97 degrees. There were some locations across the Inland Northwest that did hit the 100-degree mark last week. Moses Lake hit 100 degrees, while Pullman went to 104 degrees.

We’ll get some relief from the heat this week as temperatures will fall into the 80s across much of the region. As we get toward the end of the month, it looks like another hot spell across the Inland Northwest as highs are expected to climb back into the 90s.

The rest of the month still looks dry, so unless there is an isolated afternoon shower or thunderstorm, we’ll likely end up with a July precipitation total in Coeur d’Alene of just 0.19 inches. The normal for this month is 0.92 inches.

We hear and write about air temperature records across the globe. However, readings near or on the ground are often significantly higher. According to a study from the University of Georgia, when air temperatures start to climb into the 90s, readings on the ground could climb to as high as 140 degrees over blacktop surfaces. Temperatures on cement are around 125 degrees with red bricks having surface readings near 135 degrees with air temperatures in the 90s.

Officially, air temperatures are measured by placing thermometers inside instrument boxes or enclosures that are known as a Stevenson Screen. The design is used by most meteorological organizations around the world for over 100 years. The box has louvers that allow air to circulate around the thermometer inside and protect it from direct sunlight. The box is typically placed about 4 feet above the ground.

The hottest air temperature ever recorded was at a location in Death Valley called Furnace Creek. On July 10, 1913, the afternoon high was 134.1 degrees. However, Guinness World Records states that July 15, 1972, there was a ground temperature in Death Valley of an amazing 201 degrees. That is just 11 degrees from the temperature when water starts to boil. Also, according to an article in Science.org, high-resolution satellite data shows that two other desert locations had surface temperatures that were incredibly high. The Lut Desert in Iran and the Sonoran Desert, located along the Mexico and U.S. border, soared to an incredible 177.4 degrees at ground level between 2002 and 2019, according to a recent study.

Another interesting bit of information about extremes was the maximum temperature surface extremes. Additional information from Science.org claims that the largest temperature swing happened July 20, 2006, in China’s Qaidam Basin. In a single day, ground temperatures went from -10.7 to 136.6 degrees, an increase of an incredible 147.3 degrees.

In terms of coldest readings, there was a satellite ground temperature of -167.6 degrees in Antarctica back in 2016. This continent still holds the record for the coldest air temperature with a reading of -128.6 degrees July 21, 1983.

With more hot weather expected across our region, it’s a good idea to wear protective footwear, especially if you’re planning to walk on asphalt or other hot surfaces. And, when surface temperatures climb into the 90s or higher, it can be too hot for the paws of dogs and cats.

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Contact Randy Mann at randy@longrangeweather.com.