I saw the craziest thing today. I was on the corner of Meares and Quadra when I heard this "CROKKKCrashhh". I looked over and a massive Garry Oak limb broke off a tree in Pioneer Square and fell to the ground. The limb was as big as a tree--it was over a foot in diameter. Anyone resting underneath would have been crushed.
The dry weather can open up cracks in the crotch of trees, causing branches to weaken and fall. A "CROKKKCrashhh" is typical for Garry Oaks, which is better than hearing Aaargh!, which identifies a different type of crotch problem.