The special aspects of the environment influencing on formation of the modern extreme phenomena and processes on the Altai mountain rivers are considered in the article. On the example of the Chemal River the mechanism and reasons of hanging ice dams development that led to the flooding of the village Chemal are shown. The temperature characteristics of atmosphere, geological and geomorphological structure of the merge Chemal River with the Katun River are described. The comparative analysis of the Chemal River and Elekmonar River Valleys geological and geomorphological structure is carried out. Currently repetition of such phenomena is practically impossible, since current climatic situation in the Altai Mountains is not conducive to this. But as a residual symptom similar to the described events the formation of hanging ice dams associated with the mid-season climate warming is admissible. The forecast for repeatability of this natural phenomenon for the next decades is given. Repeatability of such events usually occurs after 20–25 years. In this regard, we can predict the development of hanging ice dams and in advance prevent the influence of the extreme processes on the social living conditions.