The National Ultraviolet Monitoring Center (NUVMC) maintains a network of Brewer Spectrophotometers that collect spectrally resolved, full sky ultraviolet (UV) irradiance values throughout the day. Using these data, an investigation into the spectral UV irradiances at several Brewer locations has been carried out by employing plant action spectra that represent a generalized response of plants to UV exposure. Analysis was performed for the year 2000 on the Chicago, Virgin Islands, and Shenandoah Brewer sites of the Eastern USA, which are of varying latitude, elevation, and atmospheric composition. The weighted and unweighted UV data grouped in SZA ranges of 10° increments is analyzed seasonally, highlighting the seasonal atmospheric differences between the sites. Results obtained in this paper suggest that UV data, when weighted with certain plant action spectra, show the potential sensitivity of plants to small changes in UV irradiances.