Scorchers aplenty headed this way

Coeur d’Alene finally reported 90-degree temperatures last week as we’re now in a period of extended warmth and dryness. The warmest temperature so far this summer has been 93 degrees, which occurred last Tuesday. It’s going to be hot through Friday as temperatures will be well into the 90s in Coeur d’Alene and surrounding areas. A few locations may even challenge the 100-degree mark this week.

The rest of July will be mostly dry, so we’ll likely end up below the .92 inch normal. Early August should start out dry with very warm to hot temperatures. Cliff and I expect to see more 90-degree days around that time and it’s possible that we could come close to or exceed the 100-degree mark. Later next month, however, it looks like we’ll see some increase in moisture.

Last week, I wrote about the intense heat wave that moved across much of the southern U.S. In addition to readings in the 90s and 100s across that part of the country, the added humidity made those areas feel much hotter, as some heat index values went above 110 degrees.

The “feels like” summer temperatures are also known as a “heat index.” It was developed by R.I. Steadman of the National Weather Service back in 1979.

The heat index is calculated by combining air temperature and relative humidity levels. For example, a 90-degree temperature combined with a 90 percent relative humidity level would push the heat index up to a very dangerous 122 degrees Fahrenheit. In the southwestern U.S., a 120-degree temperature often feels more like a dry heat, as humidity levels are very low.

The region of the country with the highest levels of heat and humidity is east of the Rockies, especially in the southern portions of the country. Depending on the age and health of individuals, prolonged exposure to heat index temperatures over 100 degrees can lead to sunstroke, heat exhaustion, muscle cramps and even heart attacks. Since the 1930s, it’s estimated that close to 30,000 American deaths have been attributed to heat wave factors.

Here in North Idaho, most of our very hot days typically have lower humidity values. Thanks to the Rocky Mountains, the humid air from the Gulf of Mexico is blocked from entering the Far West. Although we may receive some triple‑digit readings, the relative humidity levels are generally less than 20 percent, hence only a slight rise in the overall heat index.

Numerous deadly heat waves over the years have made news headlines. According to Guinness World Records, the deadliest hot spell in history occurred in Russia in 2010. During that year, there was a series of heat waves that ultimately killed 56,000 people. They died due to overheating, droughts, fires and smog. Thousands with heatstroke went to local pools and rivers to cool down and drowned.

Over the last 10 years, the U.S. and other parts of the world have experienced some of the hottest weather in recorded history. In early July 2010, severe heat gripped much of the East Coast. The Midwestern U.S. saw record-breaking heat in 2011.

The summer of 2012 produced one of the most severe heat waves in North American history. Eighty-two people were killed due to the extreme and extended heat in the U.S. and Canada. Strong thunderstorms produced a “derecho,” a powerful straight-line wind that left nearly 4 million people without power. Temperatures in the central U.S. in late June 2012 were over 110 degrees with Hill City, Kan., hitting 115 degrees.

Perhaps the most severe and deadliest heat waves to strike the U.S. occurred in 1936 during the Great Depression and in the middle of the infamous “Dust Bowl Days.” Data from Wikipedia states that many of the high temperature records that were set back in 1936 stood until the big heat wave in 2012. A reading of an incredible 121 degrees was reported in Steele, N.D., a record which still stands today. Highs of over 110 degrees were felt in Ontario and Manitoba in Canada. At Mount Vernon, Ill., readings at or above 100 degrees were reported for 18 straight days from Aug. 12-19, 1936. Over 5,000 people across the U.S. died from the deadly heat.

The hottest day ever recorded in our region was on Aug. 4, 1961. On that particular afternoon, Coeur d’Alene hit 109 degrees, our all-time record high. It was 108 degrees in Spokane. The Wenatchee airport hit 109 degrees while Ephrata and Lewiston each observed a sizzling 115 degrees.

The most torrid summer season in our region, especially during the 20th century, occurred in August 1967. Cliff’s records indicate there was an all-time record 16 days that year with temperatures at or above 100 degrees, with 45 days with readings at or above 90 degrees.

During that year, Spokane International Airport had 11 consecutive days with temperatures at 90 degrees or warmer. Lewiston observed 11 consecutive days with readings at or above 100 degrees.

More hot weather is coming, so stay cool!

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Contact Randy Mann at randy@longrangeweather.com