What species of trees?

I don't think there's a way to tell in advance unless it's a eucalyptus tree or Bradford pear. If it's either of those, a strong wind can blow branches off the tree. If it's a eucalyptus, you don't need any wind for branches to break off. same with Arizona ash. Very weak tree.

My 23 year old pecan tree inexplicably dropped several smaller diameter limbs last year, same thing, apparently healthy wood, no evidence of borers or dead zones. I then started hearing about oak trees dropping limbs unexpectedly. I did a little research and came up with something called limb drop, not a particularly helpful term but i learned this is not a new thing and can just happen without any advance signs and not necessarily because of drought stress (though that no doubt contributed here in Houston).We ended up carefully pruning the tree so no limbs overhang the street. Incidently, we had a huge pecan harvest last year and I'm at a loss to explain that other than the tree probably thought it was dying during the 2011 drought even though i pretty much used all of my water rationing allotement to keep it and one other 30+ year old tree alive. It may have been trying to hurry up and reproduce. There were more acorns than usual last year as well and the heavy nut loads probably also contributed to the limb drop.