Butterflies are sensitive indicators of climate change because temperature influences the timing of an individual's life cycle and the geographic distribution of a species. Six protected areas in the Cascade Mountains are establishing a program to monitor butterflies to learn how climate is affecting the populations. These include four sites in Washington state: North Cascades National Park, Mount Baker-Snoqualmie National Forest, Okanagan-Wenatchee National Forest, and Mount Rainier National Park.