The National Weather Service issued a severe thunderstorm warning for parts of the District of Columbia and surrounding areas in Maryland and Virginia on Saturday afternoon ahead of President Donald Trump’s highly anticipated speech to commemorate the United States’s 250th Independence Day.

Just a few hours after the announcement, Freedom 250 spokesperson Danielle Alvarez told all attendees to “evacuate event grounds and seek temporary shelter in a nearby building,” saying organizers will “share updates on programming and doors reopening.”