In recent decades, cultural eutrophication of coastal waters and inland lakes around the world has contributed to a rapid expansion of harmful cyanobacteria (blue-green algae). Potential outbreaks of toxin-producing cyanobacteria species have drawn concern from health officials and water managers given their negative ecological, aesthetic, and socioeconomic impacts. Currently, little information regarding expected summertime cyanobacteria abundance is available prior to the season. With sufficient lead time, communicating the likelihood of elevated cyanobacteria abundance may be informative for proactively managing potential threats to lake and beach safety. We developed a model to issue predictions in early June of expected summertime cyanobacteria abundance for Lake Mendota. The prediction model demonstrates moderate to good skill and an ability to accurately predict summers with above-normal cyanobacteria abundance. Associated beach closure predictions also show promise but are highly sensitive to the short observational record – a limitation directly being addressed by Clean Lakes Alliance volunteer monitors and researchers at UW-Madison.