Winter often brings severe weather to the mountains — extended rain and snow. The major challenges are very long power outages, getting trapped by blocked or washed-out roads, and damage from falling trees. After enough days of rain or snow, mudslides and floods have historically caused both property loss and most disaster-related fatalities in our area.
For a video on landslide history in the Santa Cruz Mountains: Riding the Storm — Landslide Danger in the San Francisco Bay Area
Severe Rain and Snow
Power outages: When heavy rain arrives, the first challenge is loss of power. In severe storm episodes, be prepared for a week or two without electricity. See Long Power Outages for how to plan for this.
Blocked roads: After weeks of rain, ground saturation causes washouts and fallen trees block roads. You may be trapped at home. Even if you can get out, road status changes frequently — sometimes hourly.
- Avoid travel if you don’t have to. If you get down from the mountain, you might not be able to come back up.
- Official sources (like Caltrans) are often wrong. The mailing lists will tell you what’s actually passable in your area.
- Check county road closure resources for current conditions.
- Keep your car reasonably fueled or charged.
- Carry food, water, flashlights, and a rain poncho in your car.
- Have a plan for your pets if you get stuck away from home.
- Keep one month of extra medication on hand.
Blocked roads are often caused by poorly maintained culverts. Once a strong rain hits, culverts block and roads wash away. Watch for and report blocked culverts before they become a problem.
Snow: Snow roads are impassable until plowed, and even then very slippery — Caltrans has no salt up here. Use chains. Large snow amounts are rare but our trees aren’t set up for them, causing catastrophic limb breakage that worsens road blockages and outages. Keep a snow shovel on hand.
Severe Thunderstorms
The National Weather Service defines a severe thunderstorm as producing hail at least ¾ inch in diameter, winds of 58 mph or greater, or a tornado.
Risks include lightning-caused fires, downed trees, down bursts, hail (especially dangerous for livestock), flash floods, and tornadoes.
What to do:
- Seek shelter in a substantial, permanent, enclosed structure.
- Avoid water sources, metal surfaces, and storm-damaged areas.
- Avoid flooded roadways.
- Do not use a landline telephone; cell phones are considered safe indoors.
- Watch for fallen power lines and trees.
- Do not lie flat on the ground.
- If no permanent shelter is available, take shelter in a car with windows closed.
- Avoid natural lightning rods: trees, golf clubs, tractors, fishing rods.
Floods
Rule number one: move quickly to higher ground. Flood waters carry debris, scour soil, and trigger landslides. Even 6 inches of fast-moving water can knock someone off their feet; 24 inches can carry away a vehicle.
If you must evacuate:
- Take your Disaster Supplies Kit.
- Do not walk, swim, or drive through floodwaters.
- Stay off bridges over fast-moving water.
- Keep away from waterways. If you encounter rapidly rising water while driving, turn around.
- Pay attention to barricades — never drive around them.
- Avoid storm drains and irrigation ditches.
After a flood:
- Stay out of flooded areas until authorities clear them.
- Reserve the phone for emergencies.
- Be aware that snakes and other animals may be in your home.
More information: ready.gov, NOAA Weather
Landslides and Mud Flows
Landslides move slowly or extremely rapidly — fast ones can exceed 35 mph and carry boulders, trees, and vehicles. Areas prone to landslides include: the bases of steep slopes, bases of drainage channels, old landslide zones, and hillsides with leach-field septic systems.
Be prepared:
- Learn the land around you. Watch storm water drainage patterns on nearby slopes.
- Watch for progressive tilting trees, small landslides, or debris flows as early warning signs.
- Discuss landslides with your family.
- Note that general landslide insurance is typically not available, though debris flow damage may be covered by NFIP flood insurance (fema.gov/nfip).
For more information: ready.gov