U.S. River Conditions, October to December 2020

This is an animation showing the changing conditions of USGS streamgages from October 1, 2020 to December 31, 2020. The river conditions shown range from the driest condition seen at a gage (red open circles) to the wettest (blue closed circles). A purple outer ring around a gage indicates it is flooding. As hurricane season came to a close, two final hurricanes made landfall in the south east and caused flooding: Hurricane Delta in Louisiana during early October and Hurricane Eta in the Florida peninsula during early November. In contrast, large areas experienced drought conditions at the beginning of October, including parts of the Western U.S., the Northeastern U.S. and Hawaii. As time progressed, drought conditions in the Northeast were alleviated by multiple frontal systems bringing rainfall and flooding to the East Coast through the end of December. Approximate dates of those fronts were Oct 10 – 17, Oct 25 – Nov 6, Nov 11 – Nov 26, Nov 30 – Dec 10, and Dec 14 – 31. In Hawaii, drought conditions lessened by mid-November, while in the Western U.S. drought continued through December and worsened in some areas. Parts of the Northwest were also dry in October, but Pacific moisture brought relief to the coasts of Washington and Oregon in early November. In mid-December, additional weather systems prolonged high flows in the Pacific Northwest. Note that both USGS gage height and National Weather Service flood stage levels are necessary to determine flooding conditions and were available for 38% of streamgages at the time this graphic was produced. Only publicly available data from the National Water Information System Website was used and some gages are missing gage height even when they have flow.