Technologies for generating a warning based on environmental conditions sensed in a vehicle include an in-vehicle warning system for determining whether an operator of the vehicle is present, determining whether a non-operator occupant is present in the vehicle, and determining whether environmental conditions sensed within the vehicle satisfy a reference condition threshold. Such technologies may also include performing an emergency action in response to determining that the environmental conditions sensed within the vehicle satisfy the reference condition threshold, determining that the operator of the vehicle is not present, and determining that the non-operator occupant is present in the vehicle.