Melioidosis, an infection due to the environmental bacterium Burkholderia pseudomallei, is endemic to Southeast Asia and northern Australia, with cases strongly correlated with the monsoonal wet season. We hypothesized that seasonal variation in the mode of acquisition, informed by traditional knowledge, would result in variations in disease characteristics as well as disease incidence. We explored the seasonal variation in acute, culture-confirmed melioidosis using local Aboriginal definitions of seasons in presentations to the Royal Darwin Hospital, the referral centre for the Top End of the Northern Territory, Australia. In 387 patients, we observed an increased proportion of patients with pneumonia (60%) and severe sepsis (25%) associated with presentations in the wet seasons Gunumeleng (October-December) and Gudjewg (January-March) compared with the drier seasons Wurrgeng (June August) and Gurrung (August-October) (pneumonia 26%, severe sepsis 13%). This observation supports the hypothesis that in the wet seasons there may be changes in the mode and/or magnitude of exposure to B. pseudomallei, with a shift from percutaneous inoculation to aerosol inhalation, for instance.