An aerosol-generating system comprises a liquid storage portion comprising a container holding a liquid aerosol-forming substrate and defining an opening, and a heater assembly which extends across the opening along a transverse plane. The heater assembly comprises at least one electrically operated heating element, and a first channel defines a first flow route which brings ambient air into impingement against the heater assembly. In an embodiment a portion of the first channel is arranged orthogonally to the transverse plane such that the at least a portion of the first channel directs ambient air from outside the system to impinge perpendicularly onto a surface portion of the heating element before conveying the ambient air to a downstream end.
