We found that variation in temperature and humidity significantly affected mortality rates and population dynamics of the spittlebug Deois flavopicta Stål by monitoring cohorts of diapausing eggs and nymphs for three generations. Cohorts of quiescent eggs, when exposed to increasing periods of high moisture (free water), produced higher proportions of eggs resuming embryonic development in laboratory experiments. The accumulated number of eggs resuming development as a function of days of exposure to moist conditions was modeled using a β distribution. Periods of drought and high temperatures after the beginning of postdiapause development increased embryonic and nymphal mortality. Mortality was modeled with a linear function, and in combination with the development model allowed the simulation of varying mortality rates in the newly emerged nymphal population. Comparisons with field data demonstrated a close fit to the observed and expected proportion of nymphs hatching daily. By accurately simulating natural mortality, hatching distribution and population dynamics, the model promises to be useful for managing the spittlebug in the field.