Freshwater lentic ecosystems such as lakes, ponds, and reservoirs experience marked seasonal shifts in physicochemical conditions that, in turn, regulate the abundance, composition, and diversity of their plankton communities. This review synthesizes findings from a range of tropical, subtropical, and temperate freshwater studies to examine how variables such as water temperature, dissolved oxygen, pH, nutrient concentration, and transparency fluctuate across seasons, and how these fluctuations drive succession in phytoplankton and zooplankton assemblages. Evidence is drawn from monsoon-influenced systems, high-altitude oligotrophic lakes, and large eutrophic water bodies to illustrate recurring patterns: warm, nutrient-enriched periods generally favour cyanobacterial dominance and reduced diversity, while cooler, more transparent periods support more even, diatom- or chlorophyte-rich assemblages. The review also discusses the analytical tools most commonly used to quantify these relationships, including Shannon-Wiener, Simpson, Margalef, and Pielou indices, and multivariate ordination methods such as Canonical Correspondence Analysis. Findings converge on the conclusion that plankton communities function as sensitive, rapidly responding bioindicators of seasonal and anthropogenic change in freshwater systems. The review closes by identifying methodological gaps, including the scarcity of multi-year datasets and inconsistent index selection, and by outlining implications for the monitoring and management of freshwater lentic ecosystems, particularly those under increasing seasonal and human pressure.