For real, your question makes me think of drip irrigation and greenhouse technology. I can put a fruiting vine (which needs lots of water and several-times-daily spray over the leaves) right next to a plant that gets very little water and doesn't get the leaves wet in the sunlight.
The reason? Efficient utilization of resources (drip irrigation is exempt from yard water rationing) and flexibility, in a small space. Also, can create synergistic relationships that cross microclimates. For example, honeysuckle planted next to vegetables to keep the green lace wings life-cycle within a few feet, so they perpetuate and provide larva to keep pests from eating the cucumbers.
For that to happen on a larger scale implies intent, like a greenhouse. It would be weather control for the reasons noted above, for the city or planet as a whole.
It might be done with chaos: flapping a few butterfly wings here and there make it rain right over the tomatoes the next day.
Is it artificial as intentional weather control? Maybe leftover from a lost civilization, or installed by the original colonists before technology declined. Now it doesn't work to match any obvious needs. But, the corner where it rains a little every day is a perfect place for the vegetable garden...
An alternative would be evolved control by the biosphere. But I think such a system would go after robust control and feedback mechanisms, not seemingly magic subtle effects. It takes a lot of global awareness, planning, and computation to make it work.