I believe a actually heard this limb fall early Sunday morning, even thought I live several houses further up the street. It made a heck of a racket as it came down. Photos like these provide a good reminder why we all need to watch over our trees and make sure they are maintained properly. Luckily, this limb landed in the street, doing no damage, but it imagine it landing on a car or the roof of a house. Ouch!
In this particular case, the lower part of the branch doesn’t look that rotten, although the upper end of the branch has obviously been dead for a while. We have had bit of rain and a bit of wind in the last several days, so maybe that was enough to finally bring on failure.
We are having a lot of problems like this in my area. Texas went through a horrible drought two years ago, and a moderate drought part of last year, so now, there are so many trees that have been weakened to the point of breaking off that it is heartbreaking. I see broken trees everywhere I go, even out in the “green space” behind our yard, there are broken trees. So sad, and those that are near houses and roadways are dangerous, like you say.
We had a series of wind storms a couple of years ago that was a lot like you described. I have never seen so many trees down, but most were already weakened or damaged in some way. You have to watch these things or they will come back to bite you. I try to tell people that when I see problems, but pruning a large tree can be quite expensive and so most just ignore it until it falls.