Summer heat can result in stressful conditions for Bos taurus feeder cattle, and in extreme instances these conditions can be fatal. The feedlot operator has management options available to him if he is aware of current and impending heat-stress events. Many livestock production facilities exist in environments that may differ significantly from the conditions at the closest weather station. There is a need to provide producers with heat stress information from an on-site real-time weather monitoring system. A monitoring device, referred to as a Livestock Safety Monitor (LSM), was designed around a commercial weather station (Vantage PRO by Davis Instruments, Hayward, Calif.) that was coupled to a microcomputer (TFX-11, by Onset Computer, Pocasset, Mass.). The weather station collects current weather data including temperature, humidity, wind speed, and solar radiation. The weather information is transferred to the micro-computer where the weather data is used to generate a physiologically-based stress factor. The estimated values alert the operator of current conditions that include: (1) normal, (2) alert, (3) danger, and (4) emergency categories. This article will summarize development and operating experience using the LSM.