Some of the dinosaurs must have been sheltered in valleys, water or whatever. I have a really hard time believing all the non-avian ones died out in a few hours

Some of the dinosaurs must have been sheltered in valleys, water or whatever. I have a really hard time believing all the non-avian ones died out in a few hours, but other land animals survived. A few years from blotted-out sun makes more sense. A few hours is just too hellish to think any land animals could survive, since it would have to take out all dinosaurs no matter their location, or what sort of shelter they had. Which means the same conditions would have applied to reptiles, mammals, bird ancestors, etc.