VENTURA, Calif. — For the second time in two months, wind-driven fires tore through California communities in the middle of the night, leaving rows of homes and a psychiatric hospital in ruins Tuesday and sending tens of thousands fleeing.

No deaths or serious injuries immediately were reported in the blazes burning in Southern California’s Ventura County and in inland San Bernardino County.

The Ventura County wildfire broke out Monday and grew quickly. It was fanned by strong and dry Santa Ana winds that grounded firefighting helicopters and planes.

A smaller fire erupted on the northern edge of Los Angeles, threatening the Sylmar and Lakeview Terrace neighborhoods, where residents scrambled to get out as heavy smoke billowed over the city, creating a health hazard for millions.

Eight weeks ago, wildfires that broke out in Northern California and its wine country killed 44 people and destroyed 8,900 homes and other buildings.

Fires aren’t typical in Southern California this time of year but can break out when dry vegetation and too little rain combine with the Santa Ana winds. Los Angeles has gotten hardly any measurable rain in two months.

The early official count was that at least 150 structures burned in the Ventura County fire, but it was sure to go higher.

Mansions and modest homes alike were in flames. The Vista del Mar Hospital, which treats patients with mental problems or substance abuse, including veterans with post-traumatic stress syndrome, smoldered after burning overnight. Aerial footage showed dozens of homes in one neighborhood burned to the ground and a large subdivision in jeopardy as embers could spark new blazes.