Caelumancy is the term used in this book for truly potent weather and nature magic. It's described as a crafting feat, by analogy with making magic items, but effectively the powers listed here are spells that affect areas miles across for months at a time.
There are eight different weather effects, which tend to closely resemble spells such as Control Winds or Lightning Storm, except for the greatly increased duration and area of effect.
Most of the effects listed in the book, however, have nothing to do with weather: for example, a further fifteen relate to living things, and here resemble (without just duplicating) spells like Goodberry or Plant Growth.
Five further effects are described as "boons" and do things like changing all water in the vicinity into healing potions, while five are "wracks" and are more like Contagion. Four "apocalyptic" effects create things like earthquakes and volcanoes.
In addition to the effects themselves, there are some additional feats for their creators, a section on how to dispel such powerful magic, and a fair sized selection of ideas on how to combine different effects to produce weird bits of magical geography. Also, some of this weather can apparently become sentient - presumably because magic items can - which does, at least to me, feel a little odd.
Its all pretty powerful stuff, although, like magic items, creating it requires expenditure of XPs and large amounts of money (quite what the money is spent on is unclear, however). As magical effects that can bring flavour to a game world its actually pretty good, and there are also rules for things like extreme weather.
GMs might, however, be wary of actually giving these powers to PCs. But even so, they can be used as rules for creating unusual meteorological or geographical hazards in a high-magic world. The list of effects is fairly comprehensive, and doesn't simply duplicate more regular spells. There are some good ideas here, although you might want to be careful how you use them.
[4 of 5 Stars!]