Not as common as winter wind and ice damage, but summer limb drop is well-known. Branch gets heavier on a hot day as tree draws up available water, plus weight of summer foliage or fruit causes weak branches to drop.

Ailanthus branch went down at the neighbor's some summers ago, heard and saw it.

Yes, I remember sitting on my sundeck many years ago and a branch fell off a large Douglas fir and sheared off other branches on the tree as it fell. It was a still, hot afternoon and the tree hadn't been disturbed. Another instance happened to friends. They had a huge branch on an old, big-leaf maple fall suddenly. It crashed into an area where children had been playing just minutes before.

Large poplars are prone to bursting apart on summer days.

A huge branch fell out of my honey locust last summer. No visible signs of rot.