On the timing of seasonal activity in plants and animals, the impact of climate change, and what each of us, as everyday phenologists, can do to help. Phenology is all about timing—when trees leaf out, flowers bloom, birds migrate, animals bear young and hibernate—and it is everywhere around us. This handy companionable volume shows how we are all phenologists in our own way, and how the everyday science can help us make sense of the changing seasons and our changing world. Explaining how the phenomenon of phenology is threaded through our daily lives, Theresa Crimmins points to events that occur on an annual basis in plants’ and animals’ lives in response to fluctuations in daylength, temperatures, and rainfall patterns. She also covers less visible seasonal events, such as when roots typically begin to grow or when mushrooms release their spores. On a more urgent note, Phenology describes how this seasonal activity is being affected by rapidly changing climate conditions—and why this matters. Consequently, the book invites readers to participate in documenting the timing of seasonal life cycle events—for the practice’s real benefits to mental health, but also for the good of the environment, as the data gathered can be directly helpful in supporting climate change action. Theresa Crimmins is Associate Professor in the School of Natural Resources and the Environment at the University of Arizona and Director of the USA National Phenology Network.