The answer to 'why is my dehumidifier blowing cold air' is that your dehumidifier may be malfunctioning or operating in a different mode. Dehumidifiers typically blow cool air as part of the dehumidification process, but if the air is significantly colder than expected, it could indicate an issue with the unit.
Some common causes of a dehumidifier blowing cold air include a refrigerant leak, a problem with the compressor, or the unit being in a different mode like a fan-only or energy-saving mode. If the dehumidifier is new, it may also be in a defrost cycle, which can cause it to blow cold air temporarily.