A breather assembly has an assembly body defining an airflow pathway between an assembly opening and an outside environment through environmental openings. A valve stem is coupled to the assembly body and extends axially from a proximal end to a distal end. The airflow pathway has a valve pathway laterally surrounding the valve stem. The valve body is disposed across the valve pathway having an inner perimeter coupled to the valve stem and an outer perimeter defining a sealing lip forming a releasable seal with the assembly body. The sealing lip is translatable between a closed position towards the proximal end of the valve stem and a fully open position towards the distal end of the valve stem. Greater than 96% of a flow area of the environmental openings is positioned beyond the inner perimeter of the valve body in the axial direction.