This article develops the multiple-input multiple-output (MIMO) technology for weather radar sensing. There are ample advantages of MIMO that have been highlighted that can improve the spatial resolution of the observations (for a coherent MIMO) and also the accuracy of the radar variables (in a non-coherent MIMO). These concepts have been introduced here pertaining to weather radar observations with supporting simulations demonstrating improvements to existing phased array technology. Already MIMO is being used in a big way for hard target detection and tracking and also in automotive radar industry and it offers similar improvements for weather radar observations. Some of the benefits are discussed here with a phased array platform in mind, the novel portable phased array Radar (PWR) by Agile RF Systems (ARS), which offers quadrant outputs.