ALTURAS, Calif. — Thousands of federal, state and local firefighters are feverishly attacking six major wildfires in central and far northern California, four of which grew rapidly overnight and prompted evacuations of homes, vacation cabins and recreation areas.

CalFire said the scope and intensity of the blazes burning Saturday, three of them sparked by dry lightning, are comparable to the fire activity California doesn’t usually see until the month of September.

CalFire did note the fires are mostly located in forests and sparsely population rural areas, so fewer homes are threatened with fewer evacuations.

The largest started Wednesday and had torched nearly 19.5 square miles by Saturday.