National Drought Mitigation Center


OWWLS expands to cover the entire U.S., Puerto Rico and Virgin Islands

September 26, 2023

The OWWLS website now includes weather station location data for the entire U.S., Puerto Rico and Virgin Islands.

By Emily Case-Buskirk, Communications Specialist

An expanded map of weather station locations broadens efforts to bring more transparency to the U.S. Drought Monitor (USDM) decision-making process, including highlighting coverage gaps in station-based data. 

Last year, the National Drought Mitigation Center (NDMC) produced the Overview of Weather Water Land Sites (OWWLS). OWWLS maps the location of weather stations, stream gauges, ground water monitoring stations and reservoirs that are among the dozens of datasets used in the production of the USDM. 

When OWWLS was first developed, it focused on the West, but it has now expanded to the entire U.S. This includes Puerto Rico and the U.S. Virgin Islands as part of NDMC’s work with the U.S. Department of Agriculture’s Caribbean Climate Hub and its Drought Learning Network. 

The website helps answer the frequently asked question of which stations are used in the USDM process, according to NDMC climatologist Curtis Riganti. 

“People often want to know what types of data we use, where some of our data is coming from and how they can help,” he said. “The OWWLS maps contextualize what types of data we look at as authors.” 

The USDM uses lots of inputs — including physical climate, weather and hydrological data with records of drought impacts, on-the-ground observations and local expert feedback. While it doesn’t provide an exhaustive list of data sources, OWWLS shows locations of stations that provide in situ data via several different networks. 

Categories on the map include nine types of stations. Data from many of these stations are used to assess local conditions for the USDM: 

Users can view one or more networks of stations by clicking boxes to toggle networks on and off. They also have the option to add various reference layers to the map, including watersheds, radar coverage, land use type and more. Information boxes provide additional details about the stations and reference layers.  

“For the station-based data, people see where those stations are located, so it provides helpful context for users of the map,” Riganti said. 

Conversely, the OWWLS map also shows gaps in information, helping climate service providers and partners identify areas with limited or no in situ weather or water data. This can help inform deployment of future stations and recruitment of new observers and also identifies where other data products are utilized in the USDM analysis. 

The map is static and will not tell you if stations are temporarily out of service. Most station data was originally downloaded in 2021-2022.  

The project is part of the NDMC’s one-year cooperative agreement with the USDA’s Office of the Chief Economist (OCE). 

View the OWWLS website at