This study prospectively evaluated, over 5 years, methods for detecting and predicting local influenza epidemics in Sweden using health information system data. The detection method accurately identified the start of epidemics except in 2011-2012. Peak timing prediction was satisfactory in 4 seasons but less accurate for the 2009 pandemic. Peak intensity prediction was unsuccessful for 2011-2012 and 2013-2014, which followed simmering phases. The study highlights the need for prospective evaluations and adjustments of nowcasting methods to improve accuracy for atypical influenza seasons.