Officials in weather-battered southern California have issued mandatory evacuation orders affecting thousands of people as a rainstorm threatened to unleash mudslides.

“This is a challenging storm,” Santa Barbara County Sheriff Bill Brown said at a press conference.

“Please know we do not take evacuations lightly,” he added. “We are issuing this mandatory evacuation order because there is a risk to life and property”.

The area has been lurching from one meteorological crisis to another in recent months. The largest wildfire in California history, the Thomas Fire, scorched more than 280,000 acres and incinerated more than 1,000 structures in December.

As a consequence, vegetation that helped anchor earth in place was burned from hillsides when torrential rains arrived a month later and sent mud and debris thundering into the town of Montecito. The mudslides killed 17 people, destroyed homes and set first responders scrambling to rescue people trapped in a sea of mud and debris.

With forecasters predicting that a gathering storm would dump an inch or more of rain across the Los Angeles area – the first major storm since the January mudslides – officials ordered evacuations for people living near the areas burned by the Thomas Fire and a pair of other blazes. Between 25,000 and 30,000 people live in the evacuation area.

California mudslides: in pictures Show all 9 1 /9 California mudslides: in pictures California mudslides: in pictures Emergency personnel carry a woman rescued from a collapsed house REUTERS California mudslides: in pictures Mudslides unleashed by a ferocious storm demolished homes in southern California AFP/Getty California mudslides: in pictures Emergency personnel rescue a 14-year-old girl from a house Santa Barbara County Fire Department/Handout via REUTERS California mudslides: in pictures A car piled up in debris EPA California mudslides: in pictures Emergency personnel carry a man covered in mud REUTERS California mudslides: in pictures Emergency personnel evacuate local residents and their dogs through flooded waters after a mudslide in Montecito REUTERS California mudslides: in pictures A damaged vehicle that was pushed by mudflow onto the US 101 Freeway EPA California mudslides: in pictures Los Angeles Fire Department Firefighters work admist flood waters EPA California mudslides: in pictures A semi-tractor trailer sits stuck in mud Santa Barbara County Fire Department via AP

“You should start leaving now,” Mr Brown said, adding that sheriff’s deputies were being dispatched to areas at the highest risk. “Please do not wait for someone to contact you in person in order to leave”.

Rainfall is expected to be heaviest in the early morning hours, and Mr Brown said he wanted to avoid a situation in which people are forced to flee hazard in the middle of the night.

“We want everyone to be out of the area and out of harm’s way by nightfall,” Mr Brown said. After January’s devastation, he added, “we cannot take any unnecessary chances”.

Footage shows helicopter rescue after California mudslides