A massive rainstorm continued to intermittently soak barren hillsides Glendora, Azusa and Monrovia Saturday as officials warned evacuated residents that the danger of mudslides and flooding remained very real, even as rays of sunshine peaked through the clouds.
The rain damaged to properties in Glendora on Friday afternoon and sent mud pouring into the backyards of three homes in Azusa early Saturday, authorities said. Mandatory evacuation orders for more than 1,200 area residents of the recent Colby Fire burn area remained in effect, with no estimate of when they may be lifted.
Though the storm saw a relative lull overnight, it was expected to resume dropping heavy rain on the region about 10 a.m., with showers and possible thunderstorms continuing though the afternoon, Glendora police and city officials said at a morning news conference. The storm was expected to exit the area by 9 p.m.
Glendora Police Chief Tim Staab asked evacuated residents to remain patient, and cautioned them not to underestimate the continued threat posed by the storm.
“For those residents who have been evacuated, this is getting old. We understand that. We continue to ask or our residents’ patience,” Staab said. “Out No. 1 goal is to get our residents back into their homes and, unfortunately, it’s these storms that are getting in the way right now.”
But with thunderstorms potentially on the horizon, and hillsides saturated with water and unstable, the danger remained real, the chief said.
“The experts tell us that thunderstorms are unpredictable, and they form really quickly,” he said. “They also tell us that the hillsides are so saturated that we really don’t know at this point what event can cause the hills to suddenly break loose. And once that momentum starts, you just have to get out of the way.”
The foothills near the Colby Fire burn area had received 4 inches of rain by Saturday, Glendora City Manager Chris Jeffers said.
“Rates were recorded at 1.3 inches per hour.”
Rainfall rates at or above half-an-inch per hour create serious potential for mudslide, Jeffers said.
And the NWS predicted another two inches may fall in the area by the storm’s conclusion, officials said. Even heavier rain was expected along the mountain ridge line.
The NWS issued a Flash Flood Warning for the foothill burn areas just before 2:30 p.m. Saturday as heavy rain began to fall again on the region. The warning was expected to remain in effect through 4:15 p.m.
The amount of rainfall Saturday afternoon would be crucial in determining when evacuation orders in Glendora would be lifted, Jeffers said. Those who remained in their homes were advised to stay in their homes and not attempt to leave should mud begin flowing.
And officials again cautioned residents that firefighters cannot rush into a mudslide or debris flow to effect a rescue. They must wait until the debris flow stops and drys.
The National Weather Service issued a brief tornado warning for the east San Gabriel Valley between about 3:30 a.m. and 4:00 a.m. No funnel cloud materialized, however hail as large as 1-inch fell in Walnut, officials said.
The four key debris basins near the Colby Fire were holding up well and were not expected to reach capacity during the storm, Jeffers said. When inspected at 6 a.m. Saturday, they ranged from 40 percent to 55 percent full.
Two homes in the 1100 block of Easley Canyon Road in Glendora sustained damage Friday afternoon, Los Angeles County Fire Department Assistant Chief Steve Martin said. The garage of one home was inundated with mud, while a nearby home’s backyard was flooded with mud that pressed up against the rear of the home.
City officials identified another dozen or so home where mud had flowed onto the properties, but not entered into the homes, Jeffers said. They were urged to hire geotechnical engineers to examine their properties.
Officials took note of 15 sites in the city where an estimated 200 cubic yards of mud and debris needed to be removed from roadways.
Jeffers added that the city is asking that once the storm passes, residents keep the more than 50,000 sandbags distributed during the storm in case of future potential mudslides. The denuded hillsides of the Colby Fire burn area will continue to present debris flow danger during storms for three to four years.
Residents along Rainbow Road at the northern edge of Glendora continued shoring up barriers Saturday. Some were made of metal pipes and wood, while others consisted of sandbags and tarps. Neighbors mentioned they had been contacted by city officials in February, in the wake of the Colby Fire, to discuss mitigation of potential debris flow.
Glendora residents Gary Smith used a break in the rainfall Saturday morning to take a bike ride. Looking at a barrier erected to block the flow of mud, “It looks like it did its job,” he said.
In Azusa, flowing mud along the 1700 block of Ridge View Drive, where officials expanded evacuation orders Friday, became far too close for comfort to three homes early Saturday, Azusa police Sgt. John Madaloni said. The mud flowing through the backyards reached the windowsill of one home, while it rose 2- to 3-feet high along the back of the other two.
“We don’t have any evidence that it’s actually gone into the homes, but it’s certainly accumulating outside the exterior walls,” Madaloni said.
“The damage right now is limited to cosmetic damage,” the sergeant said. Items such as fences and external stairways had been damaged, along with an avocado grove, but no structural damage had been confirmed.
Highway 39 in Azusa was shut down during a downpour Saturday afternoon due to mud flowing onto the roadway, as well as fears the K-rails placed to block slides would not hold, police said.
The evacuation zone in Monrovia, comprised of about 200 homes in the northern end of town, has sustained no reported structure damage, Monrovia police Lt. Zeke Cerecerez said.
Los Angeles County Department of Public Works Crews made quick work overnight of a mudslide the flowed onto Highland Place, just north of Hillcrest Boulevard, he said.
Officials tentatively planned to lift mandatory evacuation orders in Monrovia at 6 p.m. Saturday.
“We appreciate our residents’ patience at this time,” Monrovia Fire Department Chief Chris Donovan said in a written statement. “We are still predicting some mud and debris flows from the storms predicted by the National Weather Service this afternoon. Once those pass, we will re-evaluate the evacuation orders.”
In Sierra Madre, a rock slide on the Mt. Wilson trail prompted Sierra Madre city officials to urge residents to avoid the area late Saturday morning.

— Staff writer Grace Wong contributed to this report.