The answer to 'why is my air filter blowing cold air' is that a blocked or dirty air filter can restrict airflow and cause the air to feel colder than normal. This happens because the reduced airflow prevents the HVAC system from properly circulating warm air throughout your home.
Some common causes of a cold air filter include a clogged filter that needs to be replaced, a filter that is the wrong size for your system, or a problem with the HVAC blower motor or fan. If the filter is dirty or blocked, it can prevent warm air from circulating properly, leading to cold air being blown out instead. In some cases, a problem with the HVAC system itself may also cause this issue.