Agricultural pesticides have adverse impacts on the environment and human health. These impacts are sensitive to climate change because pest pressure and optimal pesticide application rates vary with weather and climate conditions. This study uses the Pesticide Environmental Accounting (PEA) tool and statistically estimated relationships between pesticide applications, weather and climate to compute the impacts of climate change on the external cost of pesticide applications. Using data from 32 US states, 56 crops and 325 pesticides, the current average external cost of pesticide use in US agriculture is calculated at US$42 per hectare. Under projected climate change this value increases up to $72 per hectare by 2100.