Unseasonably hot July days turned into uncomfortably warm nights over large areas of the Lower 48 states, as average overnight temperatures hit their highest level in recorded history, according to the National Oceanic and Atmospheric Administration.
Although it was the nation’s third-hottest July on record taking into account daytime temperatures, the nighttime warmth was unsurpassed — not just for July, but any month in 128 years of record-keeping, as first reported by meteorologist Bob Henson at Yale Climate Connections.
July 2022 recorded an average low temperature of 63.57 degrees in the contiguous United States, the warmest since official record-keeping began in 1880. July 2012 — with an average minimum temperature of 63.55 degrees — was the previous record holder.
A trend toward warmer nights is one of the leading indicators of human-caused climate change, reflecting both the buildup of greenhouse gases in the atmosphere and urbanization. According to Climate Central, a nonprofit science communications group, summer minimum temperatures have warmed nearly twice as fast as daytime highs. Averaged across the Lower 48 states, summer nights have warmed 2.5 degrees since 1970.
The cities with the most pronounced nighttime warming since 1970, according to Climate Central, are Reno, Nev. (17.3-degree increase); Las Vegas (9.5-degree increase); El Paso (8.1-degree increase); Salt Lake City (7.3-degree increase); and Boise, Idaho (6.9-degree increase).
During July, NOAA reported that four states posted their warmest July nights on record: Colorado, New Mexico, Texas and Tennessee; many others states saw their nights rank among the top 10 warmest.
The entire Southwest experienced its warmest nights, the temperatures boosted by humid air associated with a very active monsoon pattern.
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Increased cooling costs and demand are a consequence of such sweltering overnight temperatures. During July, the Texas power grid was repeatedly tested: On multiple occasions, the Electric Reliability Council of Texas, the grid’s operator, appealed to customers to conserve energy, and the state set a July record for its peak daily power usage.
Nighttime heat can also be extremely dangerous for human health, especially in parts of the country without reliable air conditioning or for people who cannot afford it.
Without air conditioning, the body may be unable to properly cool at night, a time when it needs a reprieve from the heat. Constant exposure to warm temperatures increases the body’s risk of developing heat stroke or exhaustion, conditions that are especially dangerous for such vulnerable groups as the elderly and the homeless.
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Maricopa County, Ariz., which encompasses Phoenix, confirmed 42 heat-associated deaths through the end of July (some of the deaths had occurred in months prior) and was investigating many other deaths in which heat may have played a role.
Warm temperatures reduce the body’s ability to progress through important states of sleep, the news magazine Wired reported. An absence of deep sleep can fuel poor decision-making, impaired performance and emotional outbursts.
Even if one can manage deep sleep on a warm night, the heat may cause the body to release an extreme amount of sweat. Excess sweating can cause dehydration, which can progress into heat-related illness.
Nowhere in the country were nighttime temperatures more persistently uncomfortable than Texas.
In Galveston, overnight temperature records were smashed throughout the month, with record-warm minimum temperatures set on 24 out of 31 days. The low temperature settled at an all-time high of 86 degrees on an unenviable six occasions.
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Dallas also saw 10 of its July overnight heat records fall, with the overnight minimum temperature also as high as 86 degrees. Averaged across the state, the mean low temperature — for the whole month — was a toasty 74.3 degrees.
Many other locations in the Lower 48 also experienced persistently muggy nights. Richmond has an ongoing record-long streak of low temperatures above 70 degrees, currently at 23 days.
While the nighttime warmth was unprecedented in the Lower 48 states, it was abnormally hot during the day, too, even if not record-setting. Most of the country had higher-than-normal maximum temperatures.
Texas saw not only its highest nighttime temperatures but also record-high daytime temperatures — with the state’s average daily temperature (between day and night) settling in at a toasty 87.3 degrees.
Dallas recorded temperatures consistently near or above 100 degrees, and San Antonio reached triple digits on all but two days. So far in 2022, San Antonio has reached at least 100 degrees on 56 days; the average number year to date is eight.
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Texas was hardly the only place to experience extreme heat in July. For a second year in a row, parts of the Pacific Northwest baked, with Oregon recording its fourth-hottest July. Six other states — Colorado, Florida, Louisiana, New Mexico, Oklahoma and Rhode Island — registered their fifth-warmest July on record.
Alaska also saw warmer-than-normal temperatures, conditions that helped to fuel wildfires across the state. Blazes across Alaska’s wilderness have burned more than 3 million acres this summer, an area larger than the state of Connecticut.
The hot July in the United States fits into a global pattern of high temperatures. July also ranked as the third-hottest for the entire planet, according to the Copernicus Climate Change Service of the European Union.
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