It's really not a new concept.
Using precipitation to mask movement, stage attacks etc. (sizeable portion of TacIntel deals with illumination and weather. No secret, just basic strategy and tactics.)
Making temporary dams to, for example, generate floods, deny enemy hydration, create droughts, or create an environment of disease.
Not surprising if the tech develops to give more immediate influence over environment.
The hubris that would be involved, and the repercussions from tampering with already highly chaotic systems however... typical homo sapient "stoopit"