Because plumbing in one apartment line had to be fixed, the main valve had to be shut off downstairs. However, the building staff then learned that the main valve was defective - and that had to be replaced. That means NO HOT WATER until about 2 p.m.
We do have cold water.
There is a second main valve with a similar problem, and that will be replaced later this week. Presumably we will get notified in advance.