Modeled heat events per 100,000 visitors in Grand Canyon National Park from 1979 through 2100.

A Poisson regression was constructed using observed heat events in GRCA from 2004–2009. Represented here is the daily average per each year of both the modeled (black line) and each year’s daily average observed events (purple points) and its 95% confidence interval (purple error bars). Additionally, the regression model was applied to 14 global climate models and projected heat events are shown in blue (RCP 4.5) and red (RCP 8.5) for each model with the 10th and 90th percentile of the ensemble marked with a dotted line.