This is the story of Operation Popeye, the U.S. Government’s project to control weather.
One such activity was cloud seeding in Vietnam intended to extend the Monsoon season. The goal was to increase the damage to roads and infrastructure to slow down the enemy forces.
You can seed the clouds by air, or by shooting materials from a cannon over the enemies heads.
The USG spent a lot of money, but the results were perhaps not as impactful as they could have been.