Extreme impacts can result from extreme weather and climate events, but can also occur without extreme
events. This chapter examines two broad categories of impacts on human and ecological systems, both of which are
influenced by changes in climate, vulnerability, and exposure: first, the chapter primarily focuses on impacts that
result from extreme weather and climate events, and second, it also considers extreme impacts that are triggered by
less-than-extreme weather or climate events. These two categories of impacts are examined across sectors, systems,
and regions. Extreme events can have positive as well as negative impacts on ecosystems and human activities.