Net radiation and potential evapotranspiration are required input parameters for most crop growth models and multi-dimensional water flow and solute transport models. ReId estimation of these parameters is a lengthy and costly process. An analytical evapotranspiration submodel (ETM) was developed as a simple means to predict daily extraterrestrial radiation, clear sky solar radiation, net radiation, pan evaporation and potential evapotranspiration from a minimal set of weather data: minimum and maximum daily temperatures, latitude and altitude of the location, ratio of actual to maximum possible sunshine hours, day of the year, and reflectivity of the surface. Such weather data sets are readily available for most locations and do not require intensive data collection. Simulations using the ETM model compared favorably to published measured data for these variables. ETM is a compact analytical model that offers rapid long-term estimates of weather data. It can easily serve as a submodel of multi-dimensional models for water flow and solute transport in soils.