The 2021 growth curve (blue dots and line) looks quite different than 2020 growth curve (orange dots and line) because the cool-season contribution is much less this year (see graph on the right).
During drought years it is often easier to observe the differences between warm-season and coolseason plants. This is especially true in July. I have been collecting biomass samples every two weeks from a grassland near Brookings which is comprised of mainly Kentucky bluegrass (coolseason), smooth bromegrass (cool-season), and big bluestem (warm-season) (see photo below). Last year this plot looked very different with much more cool-season (Kentucky bluegrass and smooth bromegrass) dominating the canopy (see photo below).
The 2021 growth curve will likely follow the generalized growth curve (depicted in red and orange in the figure to the left). I expect the peak in August and then level off after that. The dry conditions this spring/summer made for a more pronounced warmseason curve for biomass accumulation in my grassland this year because the contribution from cool-season grasses was less compared with 2020.