A month before the start of peak wildfire season in California, firefighters are already battling more than eight blazes in the southern part of the state. The fires have prompted smoke advisories in Los Angeles, led to evacuation orders for thousands of people in surrounding areas and put many people on edge less than 18 months since two devastating infernos in the region.

Dry conditions in recent months, a spring heat wave and a spell of fierce winds have all combined to make Southern California more susceptible to the rapid spreading of fires and to major damage.

Here’s what we know about some of the notable wildfires burning in the area.

Sandy fire

The Sandy fire in Simi Valley, a suburban community about 40 miles northwest of Los Angeles, has prompted evacuation orders for tens of thousands of people in Ventura County since Monday, though activity has slowed. Officials said that the fire grew significantly at first and had threatened thousands of homes because of shifting winds, steep terrain and specific fire conditions created by canyons.

It was about 22 percent contained late Wednesday, having spread to roughly 2,100 acres, and more than 850 firefighters continue to work on it. Winds were expected to lessen through the evening, but wind shifts and low humidity could contribute to periods of increased fire activity on Thursday, the Ventura County Sheriff’s Office said.

Santa Rosa Island fire

This fire, burning off the coast of California on Santa Rosa Island, is the largest active blaze. It had increased to more than 17,000 acres as of Wednesday night and was about 44 percent contained.

Dozens of firefighters were racing to save a grove of endangered pine trees on the island, which is part of the Channel Islands National Park. Nearly a dozen Park Service staff members were forced to evacuate by helicopter.

The fire began on Friday, after a man crashed his boat on the island’s rocky coast. He fired emergency flares to signal for help, which caused the wildfire.

Bain fire

The Bain fire was burning primarily south of the Santa Ana River, near the cities of Riverside and Jurupa Valley, about 50 miles east of Los Angeles.

It spread quickly after it was first reported on Tuesday, ballooning to more than 1,400 acres by late Wednesday and leading to evacuation orders and warnings for more than 39,000 people. Four civilians were taken to hospitals, including one with a trauma injury.

About 100 firefighters have been battling the blaze, which was 34 percent contained as of Wednesday night. Dried bamboo along the river helped fuel the fire, and mild winds of 10 miles per hour pushed it toward eucalyptus groves.

Verona fire

Residents in Riverside County, about 60 miles east of Los Angeles, were also dealing with evacuations and warnings from the Verona fire.

That fire, which has burned 600 acres about 40 miles southeast of the city of Riverside, is about 30 percent contained.

Soumya Karlamangla, Amy Graff, Francesca Regalado and John Yoon contributed reporting.