Last January’s ice storm led to widespread damage in the Willamette Valleymainly due to hundreds of trees falling due to wind and ice.

Experts now say residents should prepare their trees before this winter, potentially saving trees, personal property and possibly lives.

Portland City Forester Jenn Cairo said the biggest risk is not entire trees collapsing, but large branches breaking off. Thick layers of ice are usually the culprit.

“If we have extreme weather that is unusual, it can add extra weight that the tree branches are not used to and can cause them to crack or break off,” Cairo said.

Trees fell through several homes during the ice storm, including one in Lake Oswego that killed a man. Another tree fell through an RV in Southeast Portland, sparking a fire and killing one person inside.

And in Northeast Portland, three people were electrocuted when a falling tree branch brought down a power line on top of a vehicle.

Now weather experts are predicting another active winter season, with a La Niña system that typically brings lower temperatures and more precipitation.

Related: Oregon could see wetter and cooler winter conditions this year, thanks to La Niña

During extreme weather, there are some signs that a tree is at risk of falling, Cairo said. Trees that lean in a more pronounced direction, foliage that is unusually discolored and increased insect activity are all potential symptoms that something is wrong.

She also said people who care for their trees can unintentionally endanger them. For example, if all the lower branches of a tree are removed, the top of the tree acts like a sail, making it easier to blow down.

The Oregon Department of Forestry is also advising homeowners be careful where they plant new treesand first make sure they don’t pose any risk.

Cairo advised property owners to hire experts to inspect their trees and carry out maintenance before winter sets in.

“I encourage people to consider it a good investment so their trees can be healthy and stable,” she said.

Depending on the location and size of the tree, the city of Portland a permit may be required for pruning or removal.

ODF: Oregon Homeowner’s Guide to Tree Care (pdf)