Extended Data Fig. 3: Changes in summer climate on monarch summer breeding grounds.

Percent change between 1994–2003 and 2004–20018 in a, average temperatures (GDD from 3 May–15 Aug) and b, cumulative precipitation (mm, Apr–Aug) for each U.S. county included in our delineation of the monarch summer breeding range. Temporal trends over a recent 15-year period (2004–2018) in c, GDD (°C/yr), and d, cumulative precipitation (mm/yr). Positive values indicate increases or positive trends in weather variables; negative values indicate decreases or negative trends. Canadian counties were excluded from panels a and b because data limitations prevented us from including these regions in our 1994–2003 model of monarch population dynamics.