It took between 1/4" and 1/2" of ice
to cause these trees to sag heavily and threaten the nearby power lines.
This resulted in numerous power outages across metropolitan Cincinnati.
Tree limbs begin to sag and/or break with around 1/4" ice accumulation, so this is
the threshold for issuing an
ice storm warning instead of a
freezing rain advisory.
Safety Note: Ice accumulation on trees will cause branches
to fall, which can lead to injury or death. In addition, trees
falling on power lines (and sometimes the weight of the ice alone) can
cause hot lines to fall and lead to electrocution. Always avoid
large trees and power lines during an ice storm. This is another
reason not to be on the road during an ice storm.