Heat dome sweltering western US with days of record high temperatures

A heat wave for the record books is underway across the western United States, which is leading to complications with not only the drought and wildfire situation, but also the power grid in one state.

The intensity and duration of the heat is likely to put a strain on people visiting the many national parks and hiking trails across the region, as well as long-time residents who may be more accustomed to extreme conditions. This is especially true for those left without power and air conditioning due to rolling blackouts.

This past Friday evening, the California Independent System Operator (ISO) declared a statewide Stage 2 emergency due to the excessive heat driving up energy use. The ISO later declared a Stage 3 emergency and started initiating rotating power outages.

“Extreme heat throughout the West has increased electricity usage, causing a strain on the power grid. All available resources are needed to meet the growing demand,” ISO said in a statement.

As of early Sunday morning, a little over 35,000 customers were without power in California, according to PowerOutage.us.

Electricity demands will continue to be pushed to the max into at least the middle of this week as temperatures reach levels 15-30 degrees Fahrenheit above late-summer averages. Excessive heat warnings and heat advisories stretched from California and Arizona, to Washington and Idaho, early Sunday morning.

Fresno is forecast to reach the lower 110s F each day through midweek. The last time the city hit the 110-degree mark was June 20, 2017.


Sacramento could blow past its daily record highs for Monday, Tuesday and Wednesday of 106, 107 and 108, respectively, by 3 degrees or more. Cooling centers have been opened in Sacramento and other locales to help residents stay cool amid the record heat.

After tying their daily record of 98 on Saturday, downtown Los Angeles will be near this mark once again during the middle days of the week.

This summer has already gone down as the hottest on record in Phoenix with the city setting a new record for the most days with a temperature at or above 110 F. On Friday, temperatures reached 117, which tied with the city’s record for hottest August temperature that was set in 2015. Temperatures are forecast to be above 110 through at least the middle of the week in the Valley of the Sun.

“The heat could be so intense that it may affect the ability for planes to take off,” AccuWeather Senior Meteorologist Alex Sosnowski said. Travelers should prepare for flight delays, as well as some weight and baggage restrictions.

The weather phenomena responsible for the sizzling conditions is an expansive area of high pressure, which can be referred to as a “heat dome” in situations such as this. Underneath areas of high pressure, the air sinks. Sinking air compresses and heats up, causing temperatures to soar.

As this heat dome shifts orientation over the next few days, record heat will expand and retract from some areas. This includes around Seattle and Portland, Oregon, where record heat to end the weekend will be replaced with more seasonable conditions by midweek.

The searing heat will hold on longer across the interior, with widespread highs in the 90s and 100s lasting into midweek.

Outdoor activity is strongly discouraged during the midday and afternoon hours amid the pattern. If you must labor outside, be sure to take frequent breaks in the shade, wear light-colored and loose-fitting clothing and drink plenty of water or sports beverages.

Never leave pets or humans in a locked vehicle for any length of time, even if the windows are cracked open. Use caution when touching metal railings or door knobs that are in the sunlight, as they may be hot enough to cause a burn during the peak heating of the day.

The hot pattern will only intensify the widespread drought across the region, and create difficult conditions for fire crews battling the dozens of blazes burning out West.

Adding insult to injury will be localized thunderstorms with little rainfall that will only act to create an even higher fire danger.

“Monsoon thunderstorms will continue to be suppressed and storms that form will not produce heavy rain, so lightning can trigger more fires,” AccuWeather Long-Range Meteorologist Tyler Roys said. This will be especially true in portions of California, Nevada, Utah, Washington and Idaho, into early week.

One exception to this rule will be a batch of showers and thunderstorms rumbling through Northern California during Sunday morning, which prompted a rare severe thunderstorm warning for the San Francisco Bay Area.

Unfortunately, Roys and the rest of AccuWeather’s long-range experts do not foresee significant heat, drought or wildfire relief anytime soon.

Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.

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