Seattle Storm Preparedness Assessment

Frequently Asked Questions: Tree Storm Damage Risk in Greater Seattle

Q. What types of storms pose the greatest threat to trees in the Seattle area?

A. The Pacific Northwest faces several storm types that can damage trees, with winter windstorms being the most common threat. These typically bring sustained winds of 40-60 mph from November through February.

Atmospheric rivers—intense moisture streams that bring heavy rain combined with wind—create particularly dangerous conditions because saturated soil makes trees more likely to uproot.

While rare, ice storms can be devastating when they occur, adding significant weight to branches.

Summer thunderstorms with sudden wind gusts of 60+ mph can also cause damage, though they're less frequent than winter storms.

Q. Which tree species in Seattle are most vulnerable to storm damage?

A. Deciduous trees with brittle wood or shallow root systems are generally at the highest risk.

• Bigleaf Maple, while beautiful, has large leaves that catch the wind and can develop weak branch attachments.
• Red Alder and Black Cottonwood are fast-growing pioneer species with relatively weak wood that's prone to breakage.
• Pacific Willow and European White Birch also rank high in terms of storm vulnerability.

In contrast, our native conifers, such as Douglas Fir, Western Red Cedar, and Western Hemlock, are generally more storm-resistant due to their strong wood and deep root systems; however, even these can fail under extreme conditions or when compromised by disease or age.

Q. How can I tell if my trees are at high risk for storm damage?

A. Several warning signs indicate elevated storm risk. Look for these indicators:

• Dead, dying, or hanging branches, especially large ones that could cause significant damage if they fall.
• Trees leaning more than 15 degrees, particularly if the lean developed recently, may have compromised root systems.
• Co-dominant trunks (V-shaped splits) create weak points where trees often break.
• Signs of disease, like fungal growth, cankers, or unusual discoloration, weaken trees significantly.
• Trees that haven't been professionally pruned in 3+ years may have accumulated deadwood and poor structure.
• Also, consider location factors: trees within 30 feet of structures, near power lines, or in wind-exposed areas pose a greater risk to property.

Q. When should I have my trees professionally assessed for storm damage risk?

A. Schedule professional assessments annually, ideally in late summer or early fall before storm season begins. However, seek immediate evaluation if you notice sudden changes, such as new leaning, large dead branches, fungal growth, or damage from recent storms.

Trees over 20 years old, especially fast-growing species, benefit from more frequent monitoring.

If you're planning major landscaping, construction near trees, or have concerns about trees near structures or power lines, don't wait—schedule an assessment promptly.

And after any significant storm event, have damaged trees evaluated even if they appear stable, as internal damage may not be immediately visible.

Q. What preventive measures can reduce my trees' storm damage risk?

A. Regular professional pruning every 3-5 years is the most effective prevention strategy. This removes deadwood, corrects poor structure, and reduces wind resistance by thinning the canopy appropriately. In addition, these practices can help keep your trees healthy and less likely to incur storm damage:

• Proper watering and mulching keep trees healthy and better able to withstand storms.
• Address disease and pest issues promptly, as compromised trees are more vulnerable.
• For structurally weak but valuable trees, certified arborists can install cable and brace systems.
• Ensure good drainage around trees to prevent root rot and soil saturation.
• When planting new trees, choose storm-resistant species appropriate for your site conditions and avoid planting large-growing trees too close to structures.

Q. What should I do if my tree assessment shows high storm damage risk?

A. Don't panic, but do act promptly if your trees are a high risk of storm damage.

High-risk trees require professional evaluation within 48 hours to determine the best course of action. Options may include:

• emergency pruning to remove the most dangerous branches,
• installing support systems like cables or braces, or
• in severe cases, complete removal.

Temporarily restrict access under high-risk trees and document conditions with photos for insurance purposes.

If trees threaten power lines, contact your utility company immediately.

Develop a comprehensive tree management plan that prioritizes the most hazardous trees first, while considering long-term solutions such as replacement plantings with more storm-resistant species.

Remember that removing a dangerous tree is often more cost-effective than dealing with property damage or liability issues later.