Fig. 3: The pace of shifting seasons in the North American Great Lakes.

Shown are the seasonal shifts (days decade⁻¹) in the timing of (a) summer (June–August) and (b) autumn (September–November) temperatures during the satellite data-taking period (1995–2021). Positive and negative values indicate when the timing of a season has advanced or been delayed, respectively. Also shown in panel c are calculated changes to the duration of summer, which was estimated as the difference between seasonal shifts in the start of summer and of autumn (as shown in panels (a) and (b)). Positive and negative values indicate when the summer season has lengthened or shortened, respectively. Stipple markings represents regions that were not included in the analysis, either due to the presence of lake ice cover (grey points) or when lakes experienced a minimal (<0.5 °C month⁻¹) seasonal rate of change in surface water temperature (black points) during the season of interest (see Figs. S9–S15).