The answer to 'why is my central air blowing cold air' is that the most common causes are a refrigerant leak, a problem with the compressor, or a thermostat issue. If your air conditioner is blowing out very cold air, it could mean the system is overcharged with refrigerant, the compressor is stuck in the 'on' position, or the thermostat is malfunctioning and not properly regulating the temperature.
Some symptoms of these problems include the air coming out of the vents feeling colder than normal, the system running constantly without cycling off, and the compressor outside running non-stop. Solutions may involve repairing refrigerant leaks, replacing the compressor, or recalibrating or replacing the thermostat. While some minor adjustments may be DIY-friendly, it's generally best to call an HVAC professional to diagnose and fix any major issues with your central air system.