Much of California is preparing for a dual onslaught of severe weather this week, as a dangerous heat wave and heightened fire risk coincide just as millions gear up for outdoor Independence Day celebrations.

Kate Forrest, a meteorologist with the National Weather Service in Sacramento, warns that temperatures in the Sacramento Valley could climb to a blistering 115 degrees. A heat warning will take effect on Tuesday and is expected to persist until at least Saturday, heralding an extended period of extreme heat across interior California.

"This heat event will bring elevated temperatures and extreme heat risk throughout much of the region," Forrest cautioned. "It's anticipated to be a prolonged event."

Meteorologists predict the heat wave will commence on Tuesday across inland California, expanding into the Pacific Northwest and deepening into Southern California as the week progresses. Excessive heat watches, warnings, and advisories will blanket the entire Western region from southern Oregon to the low desert areas of southeast California, underscoring the broad impact of the prevailing high-pressure system intensifying the heat.

"The strong high-pressure system currently in place forces air downward, compressing and heating it," explained Forrest. "This stagnant air mass exacerbates the heat and contributes to the severity of conditions."

Governor Gavin Newsom has activated the state’s operations center in response, highlighting the state’s proactive stance in preparing for potential emergencies triggered by the heat wave.

Nighttime temperatures are expected to remain above 80 degrees F in some areas, exacerbating the risks associated with prolonged heat exposure. By Friday, much of inland California is projected to experience "extreme" conditions, according to the HeatRisk map, a tool jointly developed by the Centers for Disease Control and Prevention and the National Weather Service, which anticipates significant impacts on healthcare facilities and infrastructure.

In Oregon, communities around Medford are bracing for potentially record-breaking temperatures, with forecasts suggesting the region could surpass the 1967 record for consecutive 100-degree days. Brad Schaaf, lead meteorologist at the National Weather Service in Medford, emphasized the importance of checking on vulnerable neighbors, especially those without access to air conditioning.

However, alongside the oppressive heat, there's heightened concern for dangerous fire conditions. Pacific Gas & Electric announced preemptive power shut-offs in 10 California counties starting Tuesday due to anticipated high winds and dry conditions conducive to wildfires. Additional shut-offs are anticipated on Wednesday, potentially leaving communities without electricity during critical periods of extreme heat.

Kate Forrest highlighted the potential for wind gusts exceeding 35 mph in the Sacramento Valley, coupled with humidity levels dropping into the single digits — conditions ripe for rapid wildfire spread, particularly in dry vegetation below 3,000 feet.

"It’s a volatile situation," Forrest warned. "If a fire starts, it could spread quickly."

The timing of the heat wave and heightened fire danger is particularly concerning as communities prepare for July Fourth celebrations, often accompanied by fireworks displays. Officials urge extreme caution to prevent accidental sparks that could ignite fires in such hazardous conditions.

The California Department of Forestry and Fire Protection is currently monitoring 13 active fire incidents, underscoring ongoing threats and preparedness efforts statewide. In the Southwest, where wildfire season has already proven deadly, recent incidents like the devastating wildfire in Ruidoso, New Mexico, serve as stark reminders of the destructive potential of such events.

Climate change exacerbates these risks, with data from Climate Central indicating increased fire weather days across the Sacramento Valley over the past five decades. The frequency and duration of heat waves have also risen, according to the U.S. Environmental Protection Agency, with cities now experiencing more heat waves per year, each lasting longer compared to historical averages.

As California and the broader Western U.S. brace for this challenging weather pattern, communities and authorities remain vigilant, emphasizing preparedness and safety measures to mitigate the impacts of both extreme heat and fire danger during this critical period.