[issue] a warning

to formally or officially provide a cautionary notice or advice regarding a potential danger, threat, or undesirable outcome

The weather service issued a warning about the approaching hurricane, urging residents to evacuate.
The police department issued a warning to drivers about the increase in car thefts in the area.
The software company issued a warning to users about a security vulnerability in their latest update.
he airline issued a warning to passengers about the turbulent weather conditions expected during the flight.
The financial analyst issued a warning to investors about the potential risks of investing in the volatile market.