A weather control system, weather control matrix was a system used to alter the natural weather patterns of a planet, through a weather control grid, which acted much like a world wide environmental system.
Caldos had its weather control system installed in the mid-23rd century, when Caldos colony was established there. The net was maintained from a substation located within the colony. The net experienced several malfunctions in 2370 due to interference from the anaphasic lifeform Ronin. Ronin was using the net as a way to maintain molecular cohesion during the transition from his previous host, Felisa Howard, to his next host, Beverly Crusher. The net required a power transfer from the USS Enterprise-D and the Enterprise-D environmental controls were later affected by feedback from the transfer. (TNG: "Sub Rosa")
One of the most sophisticated weather control systems known was in place on Risa since at least the 22nd century, where it suppressed the naturally rain-soaked and dismal climate in favor of a sunny, tropical one. The system was sabotaged by the New Essentialists in 2373, with help from Lieutenant Commander Worf. Their actions were designed to make a point to the people of the Federation that the trivial pursuit of pleasure, such as on Risa, was weakening their moral fiber in the face of enemies such as the Dominion. (TNG: "The Mind's Eye"; DS9: "Let He Who Is Without Sin...") The person in charge of the weather control systems on Risa was later determined to be working for the Orion Syndicate. (DS9: "Honor Among Thieves")
During Onquanii's attempt to justify acquiring the series 5 long-range tactical armor unit that had hijacked USS Voyager in 2375, he explained that he could make more profit by selling off it's components, including its intelligence core, which when properly reprogrammed, could assist in both terraforming to planetary weather control. (VOY: "Warhead")