Among the many regions of the electromagnetic spectrum, that spanning microwaves most easily penetrates the atmosphere. Most people are familiar with radar images, produced by actively illuminating the Earth’s surface with microwaves. However, the Earth also radiates microwaves, depending on surface temperature. A great deal of information can be gleaned from this upwelling radiation, about surface temperature and at different levels in the atmosphere, rainfall, wind speed and soil moisture. NASA, in partnership with several US universities, has launched public access to passive microwave data from the Tropical Rainfall Measuring Mission and NOAA-15 satellites at pm-esip.nsstc.nasa.gov . Data go back 5 years, and include comparisons of daily air temperatures with the 20-year average.