When looking up "Touhou weather god" in Japanese on Google, this was one of the videos I found:
Probably Kanako Yasaka has the power to manipulate weather. Found this:
Kanako Yasaka
Ability to create heavenliness
Kanako's ability specifically refers to the element of Qian (乾), the "sky" of
Bagua in
Taoist philosophy. Qian is associated with creation, leadership, overtness, reliability, and acting first rather than reacting to others.
Suwako Moriya's ability to create Kun (坤, earth), refers to the opposite element.
She is at least called "wind god", so
it may be a power to manipulate wind, rain, and weather. For Kanako to be a
god of agriculture, to manipulate the wind and rain and make the soil plentiful would definitely be the quickest and easiest way to quickly and easily gather faith.
In
Symposium of Post-mysticism, it's stated that this ability of hers is still very much a mystery. Concerning what kind of power this is, since there is nothing that seems like a portrayal of this, it is not definite, but it is probably a power unimaginable to humans. After all, perhaps wind god→climate→air=sky. She has been seen altering the terrain with Suwako's help, opening holes to the underground, and even creating large structures. She helped build the
Myouren Temple, as well.