A foggy condition referred to as “low ceiling,” which causes decreased visibility, is apparently combining with at least some of the airport’s approach lights being out of service.
Currently, DCA lists “excessive delays” on its webpage. Average wait times are reportedly hovering around 45 minutes. That’s better than some of the multi-hour delays being experienced in other parts of the Northeast due to the low ceiling.
Be sure to check your flight status with your airline before heading to the airport, or check the FAA’s online flight delay information page.