Based on the above dew-point thresholds, here’s when eight cities will experience very high or extreme humidity levels, and the expected weather impact. City-by-city forecasts Washington, D.C.

Some smoke also may be drifting over the Tri-Cities from other fires in the area, according to the National Weather Service.

According to the SWPC's viewline forecast, the aurora borealis may be visible over parts of Washington, Idaho, Montana, ...

Much of the U.S. is under extreme heat warnings or advisories while New York, Philadelphia and Washington could feel like 100 degrees or more.