Why a sagging ceiling is a collapse risk
Yes. A sagging, bulging, or heavily water-stained ceiling can be dangerous, because water-soaked drywall or plaster can weaken and collapse. Report it to your landlord right away and stay out from under it.
When water collects above a ceiling, it adds weight and softens the material until it can give way suddenly, sometimes bringing down debris along with the trapped water. A ceiling that sags, bulges, or feels soft is a warning sign that should be treated as urgent, not something to wait on.
Move people and belongings away from the area, document it with dated photos, and put your report in writing. A landlord should respond to a hazard like this quickly, since a collapse can cause injury. If your landlord will not act on a dangerous sagging ceiling, a free review can help you understand your options.
This is general information about California tenant rights, not legal advice. Every situation is different.