Dangerous heat continues to bake areas of the West from Washington to Arizona

A prolonged and expansive heat wave will continue across the West into early week, resulting in record-breaking highs from the Cascades to the Desert Southwest.

Key Takeaways:

• Over the upcoming days, all-time record high temperatures will be challenged across portions of the West. Daytime highs from Washington to Arizona can range upwards of 100 F, with some Desert Southwest locations soaring above 115 F daily.

• Factors such as a recent lack of rainfall, low relative humidity levels and stifling temperatures will create an elevated wildfire threat.

• The harsh conditions can dramatically raise the risk for heat-related illnesses, such as heat stroke and heat exhaustion.

An expansive heat wave is projected to continue across the Western states through at least early week, AccuWeather meteorologists say. The pattern of intense and elevated temperatures plaguing the region is largely due to an amplified ridge in the jet stream anchoring high pressure over it with a consistent flow of warmth from the south.

"The large and expansive heat dome across the western United States will bring record heat from the deserts of Southern California stretching northward all the way into the Pacific Northwest," explained AccuWeather Senior Meteorologist Dan Pydynowski.

Daytime highs will soar above 100 degrees Fahrenheit across portions of Arizona, California, Nevada, Utah, Oregon, Washington and even Idaho.

Pydynowski highlighted that cities such as Seattle that will challenge their daily records each day through Tuesday. The heat can be particularly dangerous in some cities west of the Cascades in western Washington, such as Seattle, Olympia and Port Angeles, where many people and homes do not have air conditioning.

Across the central valleys of California and the desert and basin regions of the Southwest, highs bove 110 and even 115 are in store over the upcoming days.

The all-time record of 117 in Las Vegas was broken on Sunday as the temperature climbed to 120 degrees. This means that since records have been kept, the temperature has never been higher than this mark. Records date back to the mid-1930s. Temperatures may reach the 120-degree mark for a second time on Wednesday.

"Daily records in Vegas could be challenged or broken nearly every day from [this weekend] through at least next Thursday," noted Pydynowski.

UV indexes categorized as 'extreme'

Copious amounts of sunshine will continue to expand across the West through at least midweek, providing little relief for residents in terms of any shade gleaming from cloud cover. In the heart of the Southwest, locations like Las Vegas and Phoenix are forecast to have max ultraviolet (UV) index levels categorized as extreme for much of this week, ranging between 11 and 12.

At UV levels such as these, protection against sun damage is necessary for anyone outdoors during the midday hours. Items such as sunscreen, a hat, and loose-fitting and light-colored clothing are recommended in these situations.

Excessive heat warnings have been issued across the West, with many warnings lasting through at least midweek. The record-challenging heat will continue to pose a risk for anyone working outdoors, particularly during the prime heating hours of the daytime from mid-morning through the afternoon.

Forecasters say that a slight nudge in the pattern early this week will result in some cooling along the West coast, while locations farther inland will continue to bake in the heat.

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"Some relief is in sight for early next week as the heat dome shifts eastward, promoting a dip in temperatures along the Pacific coast. Temperatures in cities near the Pacific coast, including San Francisco and Oakland, California, are expected to dip to near historical averages for July," explained AccuWeather Meteorologist Elizabeth Danco.

Danco added that as the core of the heat dome shifts eastward into the Great Basin this week, dry conditions will again be coupled with all-time record highs from interior California into parts of southern Nevada and western Arizona.

Wildfire threat continues

As of Saturday, there were 41 active fires across Oregon and 20 active fires in California. Forecasters warn that the ongoing heat wave and drier pattern will not improve wildfire conditions across the West.

"The heat combined with dry brush and low relative humidity across the region will continue to promote the risk for wildfires to start and spread. Individuals are urged to exercise caution when using open flames and to adhere to any bans that may be in effect," highlighted Danco.

Although surface winds will generally be light across the majority of the West over the upcoming days, isolated gusts up to 30-40 mph may occur from areas spanning from southern Idaho to eastern Nevada, Utah and northern Arizona, which can cause any active fires to readily spread and pose challenges for firefighting crews.

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