Precipitation, mostly in the form of rainfall in our area, replenishes the water in our streams and aquifers that our communities use and the natural habitats need to survive. Without it, our surface water and groundwater resources would soon begin to dry up. Knowing how much precipitation we get and when it occurs helps scientists and hydrologists gain a better understanding of how best to manage our water resources.
Precipitation data used in the county's monitoring program is collected at the sites shown in the Precipitation Stations Map (PDF). Five of the sites and the ones with the longest records are part of the National Weather Service cooperative monitoring station program. Data from these sites are not made available until several months after collection.
Rainfall data measured and transmitted in near real-time are available from two sites, operated by the U.S. Geological Survey and co-funded by Loudoun County. One site is in Lovettsville and one north of Leesburg in Limestone Branch watershed. View an interactive map of the area. Because data from these stations are available in near real-time, the information is helpful to the county's Erosion and Sediment Control team and others to warn of potential problems based on the amount of rain.
Data collected from the monitoring stations are analyzed and the results presented in various ways to gain a better understanding of both recent and past precipitation characteristics and potential trends. Graphs showing long-term annual precipitation and average monthly precipitation in Loudoun County have been developed from the available data.