The Central American Locust Schistocerca piceifrons piceifrons is one of the most damaging plant pest in Mexico and Central America. The present work was carried out to evaluate the seasonal population fluctuation of S. p. piceifrons and vegetation diversity and their association with weather factors and edaphic conditions in the gregarious zone of the Yucatán Península. The study was performed in seven sites during three seasons: North-wind (December 2013), rainy (June 2014) and dry (April 2014). The locust density was sampled in transect of 100 m2, as well as the vegetation in 16 m2: plant species richness (PSR) and relative species density (RSD), and analyzed by generalized linear models. Additionally, soil samples were obtained at 10 cm depth into a 4 × 6 m quadrat, land use in the sites was classified and temperature, precipitation and evaporation of each site were obtained from the database and they were analyzed with multiple factor analysis. The population density of S. p. piceifrons was higher in the sites Panaba, Tizimin, Tunkas and Cenotillo (F= 74.3, P < 0.0001). Characterization of vegetation showed that PSR and RSD were higher during the rainy season relative to those in the dry season (F= 50.4, P < 0.0001). RSD was identified as the most important group associated with locust density (0.86), followed by isotherm/isohyets (0.63), maximum precipitation and temperature (0.60), as well as the land use (0.65); no correlation between locust density and soil characteristics was found. Locust density was positively correlated with the abundance of the grass Panicum maximum (Sr2= 0.85, PC5= 0.87). This work shows that the population of S. p. piceifrons is high in the rainy season and influenced primarily by the abundance of the grass P. maximum and the precipitation. The results indicate that surveys for early detection and control of the locust on the Yucatán Península can focus on areas with the grass P. maximum to predict risk areas and target survey efforts. Rev. Biol. Trop. 66(1): 403-414. Epub 2018 March 01.