Hiking in a wet El Niño winter: what to know before you hit San Diego trails

San Diego is heading into what forecasters expect to be a wet El Niño winter, and the city has been preparing for months. If your weekend routine includes Cowles Mountain, Mission Trails or a walk through Los Peñasquitos Canyon, the rules change a little when the rain comes. Here’s what local park officials want hikers to know.

Why this winter is different

Mayor Todd Gloria proclaimed a local emergency on Oct. 2 ahead of the El Niño season, following similar declarations by the State of California and the County of San Diego. In the City’s announcement, officials said they expect the possibility of heavier-than-usual rain, mudslides, flooding, downed trees and damage to public infrastructure. That list matters for hikers: the same saturated soil that floods streets also loosens rocks on hillsides.

What officials are watching at popular trails

Mission Trails Regional Park

City spokesperson Benjamin Cartwright told Times of San Diego that the main concerns at Mission Trails are hillside erosion and rocks shifting on saturated soil. Plan for loose footing on climbs and descents for a few days after a storm, even once the sun is out.

Something to know for winter visits: from Nov. 1 through March 31, the Father Junípero Serra Trail is closed to vehicles from 5 p.m. to 8 a.m., and the Visitor Center access road and parking close from 5 p.m. to 9 a.m. year-round, according to the City’s park hours page.

Cowles Mountain

San Diego’s most-climbed peak is steep, and steep trails are where rockfall shows up. The City said it has improved existing drains and added new ones on the steeper stretches. That helps, but it doesn’t make the trail safe during a storm.

Los Peñasquitos Canyon Preserve

This is the one to take most seriously. The preserve sits at the bottom of one of the county’s largest watersheds, and its best-known trails follow the creek. The City told Times of San Diego to expect flooding in low-lying areas and “flashy flows,” which are fast surges of water that arrive with little warning. Fires near the canyon earlier this year also left burned slopes, which shed water and debris faster.

How bad can it get? After storms in 2019, a ranger told NBC 7 that the creek, normally 2 to 2½ feet deep, had risen to about 11 feet, with knee-deep water on sections of trail. Rangers said it could take a week or more of sunny days to dry out.

The City and County own and manage the preserve together. For trail status, the City’s preserve page lists the Park Ranger Office at 858-538-8066. The parking areas close from sunset to sunrise.

The City’s advice is simple: stay out of open space areas during any expected storm.

How to check before you go

• County parks: The Park Notices and Closures page has a Storm Closures section. The County says storm closures can last from a few hours to several days and may include trails, staging areas and roads. It recommends calling the park office for the latest conditions.
• City open space: Check for posted signs at the trailhead, and call the ranger office for preserves like Los Peñasquitos.
• Emergency alerts: Sign up for AlertSanDiego, the county’s official alert system. The City also keeps its storm resources at sandiego.gov/elnino.

A few spots close for water reasons beyond rain. The County notes that some San Elijo Lagoon trails can close during high tides, and that Monument Mesa Road in Tijuana River Valley Regional Park may close when trails flood (campground staff can confirm road conditions at 619-205-1680).

Trail etiquette after the rain

Muddy trails tempt people to step to the side, and that’s how trails get wider and habitat gets trampled. Rangers at Los Peñasquitos have said that walking around flooded sections creates new paths through protected areas and that unofficial “fixes” can delay real repairs. Rangers said people found on closed trails would likely be asked to leave, and some could be cited.

A simple rule of thumb: if your shoes are sinking, or the trail is running with water, turn around and save it for another day. Your favorite trail will still be there, and it’ll be in better shape when you come back.

Common questions

Are San Diego trails closed when it rains?

Not automatically. Many stay open, but County Parks may close trails, staging areas and roads during and after storms, and the City asks people to stay out of open space parks when storms are expected. Check the County’s closures page or call the park before you go.

How long do trails stay closed after a storm?

The County says anywhere from a few hours to several days, and low-lying areas can stay inaccessible for several weeks after heavy rain or back-to-back storms.

Is Cowles Mountain safe after rain?

The City has added and improved drains on the steeper sections, but rockfall and slides are the main risk on steep trails after heavy rain. Give it a day or two to dry, and skip it during storms.

Getting your home ready for storm season too? Read our guide to what high tides mean for your home, and see why mosquitoes show up after the rain.

Top photo: Mission Trails Regional Park, by Christopher-Lorenzo C on Unsplash.