June 14 (UPI) -- The magnitude of the heat across the western United States through the coming week will be one for the record books, according to forecasters.
And it's not just how hot it will get that will set this particular heat wave apart from others the region has frequently endured in the past -- it's how long it will last.
The hot pattern could set dozens of new daily record highs through the middle of June, in addition to potentially setting new all-time high marks for the month as a whole in some locations.
The intense heat has prompted the National Weather Service (NWS) to issue excessive heat watches and warnings throughout California, southern Nevada, western and southern Arizona and Utah. Many of these alerts last through Friday, June 18.
The hot air began to build on Sunday with records falling from Arizona and California to Wyoming and Idaho. One of the longest-standing records to be broken was in Salt Lake City, where the mercury rose to 102 degrees Fahrenheit, breaking the date's record of 100 from 1918.
June 13, 2021, is now also the earliest instance of a 102-degree temperature in Salt Lake City, breaking the previous record from June 15, 1974, according to the NWS.
Other record highs fell in Stanley, Pocatello and Idaho Falls, Idaho; Safford, Tucson and Nogales, Arizona; Rock Springs and Laramie, Wyoming; and Anaheim, California, as highs in the 80s, 90s and 100s were recorded. Such temperatures are more typical of July and August.
AccuWeather meteorologists expect these mid-summerlike conditions to persist as the jet stream bulges northward and keeps the hot air flowing into the region.
"The heat will only become more intense through the week," AccuWeather Meteorologist Mary Gilbert said.
In an area of the country that is no stranger to hot weather, the intensity and longevity of this heat wave is what has forecasters particularly concerned this go-round. Highs can trend as much as 15-25 degrees Fahrenheit above normal at the peak of the heat wave.
"No easy way to say this, so we'll just cut straight to the chase: it's going to be very hot for a long time [this] week," the NWS office in Salt Lake City said on Twitter.
AccuWeather meteorologists are predicting Salt Lake City to tie or break its record highs each day through Wednesday, with high temperatures near or topping 100 degrees.
During Monday and Tuesday, Salt Lake City's all-time record high for June of 105 could be in jeopardy of being tied or broken. The city's record for consecutive triple-digit days of four will also be challenged.
In Phoenix, the NWS called the magnitude of the upcoming heat "rare, dangerous and deadly." Saturday was the city's first 110-degree day of the year, and AccuWeather meteorologists say it's only going to get hotter.
Through at least Friday, the Valley of the Sun is forecast to challenge or fully break the high-temperature record each day with highs solidly in the 110s. The city has a significant chance to tie or break its record for consecutive 115-degree days of four.
This record was achieved in 1968, 1979, 1990, 1995 and twice in 2020, according to the NWS. On average, it takes Phoenix until the first week of July to achieve a high temperature in excess of 115 degrees.
Las Vegas is another traditionally hot city that will experience the heat to another level through the middle of June. Tuesday through Thursday, Sin City is forecast to approach or reach 115 degrees and challenge record-high temperatures that date back to 1940.
"It is unusual for Las Vegas to reach above 115 degrees, even in the hottest part of summer. The official reporting station for the city has documented temperatures above 115 degrees in only 21 of the last 73 years," Gilbert said.
"Make sure your outdoor recreation plans are heat safe! With climbing temps, you may be putting yourself at risk if you aren't prepared. Adjust times to cooler parts of the day & pack lots of extra water!" the NWS in Las Vegas advised on Twitter ahead of the heat wave.
Death Valley, California, another location familiar with triple-digit temperatures, will absolutely scorch by the middle of the week, according to forecasters. From Wednesday through Friday, the high temperature could come within 10 degrees of the all-time high ever recorded at Death Valley -- a scorching 134 degrees in 1913, according to the National Park Service. At the very least, each day's record high is likely to be broken. Wednesday's and Thursday's record highs of 123 and 122, respectively, have stood since 1917. The average high for the middle of June in Death Valley is around 110.
"With this abnormal level of heat across the entire Southwest this week, cooling demands will increase, which may put a strain on the electric grid, as well as residents' wallets," Gilbert said.
Experts urge visitors and even long-standing residents who may be more accustomed to such extreme conditions to limit outdoor activity to the coolest times of the day, drink plenty of fluids and spend as much time as possible in air-conditioned buildings.
And the heat won't just be sequestered to the Southwestern states, with record warmth expected as far north as Montana, according to forecasters.
In fact, Billings, Montana, is expected to hit 104 on Tuesday, which would shatter the 1987 daily record of 98.
Clouds and showers
Farther west, however, clouds and showers from a slow-moving storm system will keep the coastal areas of the Northwest cool.
It may not be completely dry across the interior West either during the spell of heat.
A few pop-up thunderstorms are possible over the higher mountains in Wyoming, Colorado, New Mexico, Utah and Arizona this week, according to AccuWeather Senior Meteorologist Tyler Roys.
"While bringing beneficial rain to some drought-stricken areas, these pop-up thunderstorms may also pose a risk for igniting new fires," Roys said.
The risk for wildfire spread will increase amid the heat wave, even in the absence of any lightning strikes. With fuels like grass or brush so dry, the smallest spark may quickly spread into a large wildfire.