Most fires are caused by humans — by power lines falling, by sparking mufflers dragging on the pavement and by gardening equipment, for example — although few are intentionally started.
In past decades, California’s fire season reached its peak in late summer and fall, further propelled by strong winds that arrive in October and November. But recent studies have shown that the season is now extending earlier into spring and later into winter.
Climate change, neglected forests and the death of 130 million trees in the state have also combined to increase the potential devastation of each fire. Five of the six largest fires in recorded California history occurred last year.
Gov. Gavin Newsom last week expanded a drought emergency, the second major drought of the past decade, to most of the northern half of the state and large parts of the agricultural Central Valley. The declaration directs authorities to retain higher levels of water in upstream reservoirs for release later in the year.
Reservoirs in many parts of the state look like scenes from a climate change documentary, with formerly submerged tree stumps now appearing above the water line. Satellite imagery shows an exceedingly thin layer of snow on the Sierra Nevada, the state’s crucial reservoir of water. The volume of water held in the snowpack is just 5 percent of normal, according to the Sacramento office of the National Weather Service.
Last month was the driest April in Sacramento since official record keeping began in 1877, the office said.