The traditional equation for the linear instability threshold phase speed vph of Farley-Buneman waves in terms of electron and ion temperatures is vph2=(&ggr;eTe0+&ggr;iTi0)/mi, with &ggr;e and/or &ggr;i taken to be identically unity or 5/3, depending on whether the electrons/ions are assumed to behave isothermally or adiabatically. A generalized fluid treatment of Farley-Buneman waves, using Grad's 8-moment method for the electrons with isothermal ions, has allowed us to investigate systematically the influence of two classes of electron thermal effects on the threshold phase speed not normally considered in fluid approaches. The first class is associated with the electron temperature dependence of the electron-neutral momentum transfer collision frequency, which leads to coupling between momentum and heat flow (thermal force and thermoelectric effects). The second class is electron-neutral collisional energy exchange and, in particular, the contribution of inelastic processes to electron energetics. A dispersion relation is presented in a form that makes manifest its consistency with earlier, less general treatments. From this dispersion relation an equation for vph2 is obtained, and in turn, an equation for an effective &ggr;e is presented. Our analysis of this equation leads to simple criteria that indicate when electron-neutral collisional energy exchange becomes important, as well as when departures from isothermality become significant. While our formalism is valid for Farley-Buneman waves in both the equatorial and auroral electrojets, our computed results focus on the auroral situation, allowing for background electron temperatures Te0 ranging from the neutral background to 1000 K.¿ 1997 American Geophysical Union