Brown or discolored water is alarming to see, but it's usually explainable — and fixable.
If the water was recently shut off for repair work nearby, or a hydrant was flushed on your street, sediment in the pipes can get stirred up temporarily. Running the cold tap for a few minutes often clears it.
Brown water only on the hot side usually points to rust or sediment building up inside the water heater tank itself, especially in units over 8-10 years old.
This is more often a sign of corroding galvanized pipe somewhere in your home's plumbing. As the interior of the pipe rusts, it sheds particles into the water supply.
Avoid drinking the water until it clears. If it doesn't clear after running the tap, or it keeps coming back, have a plumber check the water heater and, if needed, evaluate whether a repipe makes sense.
Dealing with this in your home? Repiping is available 24/7 across California.