This is the first book in the Capitol trilogy. The trilogy is essentially a 3-volume novel. Reading Forty Signs of Rain by itself is possible, but not as satisfying for many people. By itself, the book also has little SF content.
The book begins with an introductory explanation of the implications of global warming on Earth's ice caps and the resulting effects on the Gulf Stream. However, well into the book there are limited references to immediate effects for the characters. Washington DC seems to be too warm for early Spring. When we meet the embassy people for the tiny island nation Khembalung we hear of rising ocean levels which have begun to some degree and are expected to increase. Towards the end of the book, an extraordinary storm results in flooding in Washington, DC. There’s more in the following books, but that’s it for this volume.
Mostly, we have an extended introduction to various characters:
Anna is Frank's boss at the National Science Foundation (NSF). Also Charlie’s wife. She befriends the Khembalung embassy staff.
Charlie is an environmental expert associated with Senator Chase. Also Anna’s husband. He takes care of their baby during the day.
Joe is Anna and Charlie’s baby
Frank is working at NSF. He worked at the University of California at San Diego and at Torrey Pines biotech startup.
Senator Chase is a politician willing to work on issues to some degree, but too politically pragmatic to act as strongly as Charlie wishes.
Members of the Khembalung embassy become friends with Anna and Charlie.
Frank is inclined to view what people do as an expression of hominid behavior on the savannah translated into a modern setting. There are other discussions of social behavior in the book. Often there is some reference to how it relates to primate behavior, but generally not as strongly as Frank's view. There's discussion of voter attitudes towards business and government, how the Prisoner's Dilemma relates to driving and other social interactions...
There's a portrayal of the process by which the NSF selects research proposals to support.
We see characters dealing with conservative climate change deniers.
We get a view of the various relationships between government, science, economics and tech startup companies
The story apparently takes place in the near future. But the actual science fictional elements are limited to unusual weather (presumed to be related to climate change) and some biotech which is presumably speculative (but not so clearly futuristic). Definitely not a strong SF feel.
By itself, Forty Signs Of Rain is more to be read for the character material, for the peek into the operations of NSF and biotech firms, for a view of the difficulty in getting government to act, and for the various discussions on politics, economics, science and psychology.