Blistering heat and dangerous fire weather are threatening much of the West and the Great Plains — particularly in California, Idaho, Montana and Oregon, where thousands of firefighters are battling several massive wildfires.

Threat level: The long duration of record-setting temperatures is affecting a broad region facing unprecedented drought. This, plus weather systems that are encouraging the air to rise to set off thunderstorms, is leading to perilous wildfire risk situations across multiple states.

The big picture: In total, 15,100 wildland firefighters and personnel were assigned to incidents across the country on Thursday morning.

• They were fighting 71 large fires in eight states — mostly in the West — that have so far burned more than 496,900 acres, according to the latest information from the National Interagency Fire Center.
• "Critical windy conditions are forecast for parts of the Great Basin, Northwest, Northern Rockies and California. Excessive heat warnings and heat advisories are in effect for California, Nevada and Oregon. Red flag warnings are in place for hot, dry and windy conditions in parts of Idaho and Wyoming," the NIFC said on Thursday.
• A fuels and fire behavior advisory has been in place for northern California for several days now due to dry fuels and the potential for extreme fire behavior with the hot, dry and windy weather pattern, as the historic heat wave strains the state's energy grid.

What's happening: Fresh evacuation orders were issued late Wednesday over the Fairview Fire that's killed two people, as the blaze near Hemet swelled to nearly 20,000 acres at 5% containment.

• Cal Fire Chief Josh Janssen told reporters earlier Wednesday the fire was continuing to "outpace our efforts and burned actively on all flanks," per the Los Angeles Times.
• The Mosquito Fire near Foresthill, some 52 miles northeast of Sacramento, saw mandatory evacuation orders issued for Placer and El Dorado Counties as it burned uncontained across more than 6,8800 acres as of Thursday morning.

Meanwhile, in Montana Sanders County declared an emergency due to three wildfires near communities in the state's northwest, per Montana Public Radio.

By the numbers: Firefighters have reported fighting 28 large fires in Idaho, 12 in Montana and 11 in Oregon.

• Eight large fires are burning in California and also in Washington, another two are raging in Wyoming, while Utah and Texas each have one big blaze.

Driving the news: Climate change is making this heat wave hotter, more expansive, and longer lasting than it otherwise would have been. It is drying the environment out even more, making it more likely to burn.

• Any fires are more likely to exhibit extreme fire behavior, including forming towering pyrocumulus clouds that are a telltale sign of dangerous conditions on the ground.
• Excess heat can also be challenging to firefighters, who face an increased risk of heat illness while protecting homes and holding flames back from people rushing to evacuate at risk areas.

What to expect: "Critical Fire Weather conditions" were forecast throughout portions of the Intermountain West and Central Plains, the National Weather Service said on Thursday morning.

• Above average temperatures combined with low relative humidity and gusty winds ahead of a cold front "will allow for conditions supportive of new wildfires to form and existing fires to spread uncontrollably," the NWS warned.
• The NWS' Storm Prediction Center issued a Critical Fire Weather area for Thursday over central Idaho, parts of central Nebraska and southeast South Dakota.
• Red Flag Warnings were issued from Idaho to the central Plains, "as well as throughout the Pacific Northwest, where elevated fire weather conditions exist on Friday," the NWS noted.

Editor's note: This article has been updated with new details throughout.