Heat versus cold

With the summer season in full swing, we’re hearing about the extremely hot weather across the U.S., especially in the eastern portion of the country. June was a warmer-than-average month across the Inland Northwest. Despite average temperatures as much as 10 degrees below normal levels last week, the average reading for June, when combining the high and low temperatures, was about 4 to 5 degrees above normal.

The big heatwave east of the Rockies last week led to widespread strain and damage to public infrastructure. For example, according to an article on CNN, roads buckled from South Dakota to Iowa. Public trains were canceled due to the hot weather, with fears of warping rail tracks. High humidity levels and record-breaking air temperatures made life very difficult for residents across much of the eastern portion of the country as heat indexes were above 100 degrees.

Speaking of record heat, normally mild to warm parts of the country, such as northern New England, reported record-breaking temperatures. Last Tuesday, Augusta, Maine, hit 100 degrees, with other major cities in the region topping the 100-degree mark.

As temperatures get hot, any additional humidity in the air can make it feel even hotter, which was the case across a large portion of the U.S. east of the Rockies. The feels-like summer temperatures are also known as a “heat index.” This 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% relative humidity level would push the heat index up to a very dangerous 122 degrees. In the southwestern U.S., a 120-degree temperature often feels more like a dry heat as humidity levels are very low.

Here in North Idaho, most of our very hot days typically have lower humidity values. Thanks to the Rocky Mountains, much of 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%, hence only a slight rise in the overall heat index.

With a warmer Earth, major and longer-lasting heatwaves have become an increasing concern for infrastructure and human health. While heat-related deaths receive considerable media attention due to heat waves, many research studies have shown that cold-related deaths have historically been far more numerous. But the balance between heat and cold fatalities is showing signs of shifting toward the hotter side in ways that require renewed attention from public health authorities.

It's difficult to get precise estimates on the exact mortality rate of heat versus cold. For example, from extreme heat, people can succumb to conditions such as heat or kidney disease, respiratory infections and other ailments after being exposed to extreme heat. A major study published in The Lancet in 2021 analyzed temperature-related mortality data from 2000 to 2019. It is estimated that about 9.4% of deaths were related to temperature. The vast majority of them, 8.5%, were related to cold, while 0.9% were due to extreme heat. This means that cold has contributed to nearly nine times more fatalities than heat over the two-decade study period. In colder climates, prolonged exposure to low temperatures increases the risk of hypothermia, respiratory infections and cardiovascular strain, especially among the elderly and vulnerable populations.

In the United States, however, data from the Centers for Disease Control and Prevention and the National Weather Service indicate that cold conditions have generally been deadlier than heat. From 1999 to 2019, the average number of cold-related deaths per year was estimated to be between 1,200 and 1,600, while heat-related deaths ranged from 700 to 1,300 persons.

In terms of our local weather, temperatures are expected to be in the 90s across many locations through the middle of the week. The long-range computer models are indicating that a strong ridge of high pressure will continue to dominate the western U.S. through at least the middle of July. There is a chance we could see some isolated showers or thunderstorms popping up over the next several weeks, but most of the activity is likely to be over the mountains.

Temperatures are also expected to be very warm to hot. There are signs that readings may be near or above the 100-degree mark in the Spokane and Coeur d’Alene region next week.

Longer term, Cliff and I believe that the first half of the summer season will continue to be warmer and drier than average. However, there is a chance that the second half will be a little wetter as weather patterns in this region are notorious for flipping from one side to the other. Some of our dry summer seasons have been followed by a wetter-than-normal fall and early winter. Stay tuned.

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Contact Randy Mann at [email protected].