Abstract: The evidence of negative effects in the artificial precipitation enhancement experiments in the past and the caused conditions and reasons have been analysed and reviewed briefly. It is shown that the zero or negative effects may be caused by the unsuitable synoptic situation and cloud selection criteria, inappropriate seeding agent and delivery technique. Therefore, the suitable targeting cloud selection, appropriate seeding agent and delivery technique in the cloud seeding operations are needed for precipitation enhancement. The possibility of crippling local heavy rain artificially has been also explored based on the inspiration from the appearance of negative effects mentioned above, showing that is an interesting research field with great potential social and economical benefits