Santa Ana Winds: What They Are and How to Prepare

Santa Ana winds are warm, very dry winds that blow from the inland deserts toward the coast of Southern California, usually in fall and winter. In San Diego County they push humidity down, temperatures up and fire danger sharply higher, which is why the National Weather Service, Cal Fire and SDG&E all watch them closely.

Preparing for them is mostly about doing a few things before the season instead of during a windy night: sign up for county alerts, learn your evacuation zone, clear the area around your home and plan for a power shutoff. The rest of this guide explains the weather, the warnings and those steps in order.

What Santa Ana winds are

On a normal San Diego day, air moves from the cool Pacific toward land. That onshore flow brings the marine layer and the mild temperatures the region is known for.

During a Santa Ana event, the pattern reverses. High pressure builds over the Great Basin and the high deserts to the northeast, while pressure stays lower along the coast. Air flows from high to low, so it pours southwest, through mountain passes and canyons, and down toward the ocean. As that air sinks, it compresses and warms, and its relative humidity drops. National Weather Service forecasters in San Diego have described the setup this way in public briefings, as reported by KPBS.

You notice it fast. Skin and lips dry out, static shocks get more frequent, the sky turns a deep clear blue, and the ocean breeze disappears. Some days, the coast is hotter than the inland valleys usually are.

Where the wind is strongest

The winds are funneled by terrain. Mountain passes, canyons and the western foothills often get the strongest gusts, while the immediate coast may only feel a warm breeze. Inland communities in the foothills and the backcountry tend to see the most damage and the most power shutoffs.

When the season runs

Santa Ana events are most common between fall and early spring. Research behind the Santa Ana Wildfire Threat Index, published by the University of California, found that fire risk from these winds is highest from late September into November, before winter rain soaks the brush. A Santa Ana in January can still drive a fire if the season has been dry.

The warnings and what they mean

The National Weather Service office in San Diego issues several products during Santa Ana events. Each one means something specific.

The Santa Ana Wildfire Threat Index

The U.S. Forest Service, SDG&E and UCLA developed the Santa Ana Wildfire Threat Index, which rates upcoming Santa Ana events by their potential to produce large fires, according to the federal Climate Resilience Toolkit. The index uses a six-day forecast and sorts events into levels, starting at Marginal. It is a good tool for looking ahead a few days, but it does not replace official warnings.

Public Safety Power Shutoffs

When wind and dry vegetation make it dangerous to keep certain power lines energized, SDG&E can turn off power in specific areas. These Public Safety Power Shutoffs are concentrated in high fire-risk areas, mostly in East County, North County foothills and the backcountry. SDG&E posts notices and maps at sdge.com/psps and says it notifies affected customers in advance when it can.

A shutoff can last from a few hours to several days, because crews have to inspect lines before power comes back. If you rely on electricity for medical devices, refrigerated medication or mobility equipment, contact SDG&E ahead of the season about its programs for customers with medical needs, and talk to your doctor about a backup plan.

How to prepare before the season

Most of what helps happens weeks before the first Red Flag Warning.

Sign up for alerts

The County of San Diego runs AlertSanDiego, which sends emergency notifications by call, text and email. Listed and unlisted landlines are already in the system, but cell phones, internet phones and email addresses have to be registered at ReadySanDiego.org. The City of San Diego's Office of Emergency Services also points residents to it. Register every adult in the household, plus anyone you care for who lives alone.

Know your evacuation zone

The county uses Genasys Protect (formerly Zonehaven) to divide the region into evacuation zones. Look up the zone for your home, your workplace and your kids' schools on the Genasys Protect website or app, and write those zone names down. During an evacuation, orders are announced by zone, and you won't want to search for yours with a phone at 10 percent battery.

Harden the area around your home

Cal Fire's defensible space guidance focuses on the first few feet around a house, where embers land and ignite. Clear dead leaves from gutters and roofs, move firewood and patio cushions away from walls, and trim branches that hang over the roof. Check your city or fire district for local brush management rules, which can be stricter than the state minimum.

If you are rethinking your yard, keep the county's water-use rules in mind; our guide to water-use rules in San Diego County explains where to check what applies to your address.

Plan for the power going out

Charge phones and battery packs when a wind event is forecast. Keep flashlights where you can find them in the dark, and skip candles on windy nights. Know how to open your garage door manually. If you use a portable generator, run it outdoors, away from windows, because generators produce carbon monoxide.

During a Santa Ana event

Once the wind arrives, the goal is to avoid starting a fire and to stay ready to move.

Don't mow dry grass, use power tools on brush, or tow a trailer with dragging chains; sparks are enough. Many parks and preserves restrict use during Red Flag Warnings, and some trails close. If you were planning a coastal hike, check conditions first; our guide to the Torrey Pines hike covers where to look for current trail rules.

Bring in or tie down patio umbrellas, trampolines and trash bins. Park away from big trees if you can. Keep pets indoors.

Wildfire smoke can travel far from the fire. When air quality drops, keep windows closed, run any air filtration you have, and follow advisories from the County of San Diego and the San Diego County Air Pollution Control District. People with asthma or heart conditions should follow the plan they have made with their doctor.

If you receive an evacuation warning, get ready to leave. If you receive an order, leave. Don't wait to see flames.

After the wind dies down

Downed power lines are the main hazard. SDG&E's advice is to assume every downed line is energized, stay away from it, and call 911 and SDG&E. If a line falls on your car, stay inside. Check gutters and the roof for embers or debris if there was fire nearby. Restock your go-bag.

Santa Anas also tend to end with a quick return of the ocean breeze. On a lot of fall days, that means a warm, clear coast where the beaches feel like summer again. If you want to take advantage, our guide to choosing a San Diego beach helps you pick one.

For more on everyday life in the county, from utilities to weather, see our Living in San Diego section.