Cal Fire confirmed on their Twitter Page on Monday that the Mendocino Complex Fire has killed a firefighter from Utah. He was airlifted to a local hospital, where he succumbed to his injuries.
"The Mendocino Complex Unified Incident Commanders from CAL FIRE, and the United States Forest Service are deeply saddened to report the death of a firefighter on the Mendocino Complex", CAL FIRE sad in a statement. "More information will be released as it becomes available".
Eight civilians have also been killed in the blazes across the state.
The fatality marks the sixth firefighter to be killed in California's wildfires this year alone.
This summer ranks as one of California's worst fire seasons, as numerous blazes burned with extraordinary intensity and speed across the drought-parched state, stoked by erratic winds and record temperatures.
The Mendocino Complex Fire, which consists of both the Ranch and River fires, has burned through about 350,000 acres in Mendocino, Lake and Colusa counties.
Though temperatures had dropped from their triple-digit highs in recent days, they were expected to stay above 32C through Friday.
Fire crews are working tirelessly in sweltering conditions, battling multiple fires.
The reopening of Yosemite Valley, by far the most heavily touristed area of the park, came as firefighters continued to make slow, steady progress containing the last hot spots of the Ferguson Fire, which erupted July 13 at the edge of Yosemite. Then it's time for the autumn bushfire season when Santa Ana and Diablo winds can whip up flames in Southern and Northern California respectively (see: Last year).