The HADS website run the by NOAA and the National Weather Service is a huge repository for tons of data gathered by their precipitation and stream flow gages. Unfortunately, this website can be rather difficult to navigate. But using this map layer will provide easier and geographically-oriented access to this website's gold mine of hydrologic data.
Purple points on the map represent gage stations that record both stream flow and rainfall data, green points represent stations that gather only streamflow data and yellow points lead to stations with only rainfall data. When you click on these points, you are provided with a number of links that lead to graphs and tables.
Note that many of the stream gages featured in this layer actually refer to USGS stream flow gage stations that are also available as a map layer here. The streamflow graphs accessed through the HADS map layer only report stream flows in stages and not in CFS. The precipitation readings show the precipitation that has accumulated over a long period of time (probably reset annually?). If a graph or table had a reading of 31.2 twelve hours ago and is currently reading 32.7, then 1.5 inches of precipitation has fallen in that 12 hour period. The units on the Y-axis of the precipitation graphs refer to inches of precipitation. For more information about the webpage that opens when you click on the 'More…' link under Tabular Data, go here.
This map layer curently has 10,322 gages located in all 50 US states, Puerto Rico, British Columbia and the Yukon Territory. Click here to download.