Hosted by the University of Illinois at Urbana-Champaign, The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) is an excellent resource for precipitation data. Network collaborators include the State Agricultural Experiment Stations, U.S. Geological Survey, U.S. Department of Agriculture, along with many other government agencies, universities and private organizations. "The purpose of the network is to collect data on the chemistry of precipitation for monitoring of geographical and temporal long-term trends." At this site, users may search out weekly and daily precipitation chemistry data, isopleth maps, mercury deposition data, annual and seasonal deposition totals, and much more. Users should note, there is a five to six month time lag between data collection dates and data availability on the Website.