Great American State Fair Attendees Accost National Guard, on Video

It's getting hot in Washington, D.C., and we're not talking about the weather ... the streets are heating up as tension rises between citizens and the National Guard.

Our TMZDC is out in the nation's capital for America's 250th birthday on Saturday ... and they captured this clip of Great American State Fair attendees expressing their distaste for the authorities keeping them out of the event.

If you don't know ... the event was evacuated just a few hours ago due to the intense heat -- one of many Freedom 250 events that had to be canceled because of the unbearable weather.

Welp, these attendees didn't take it so well ... butting heads with the National Guard.

Check it out ... there's some booing and chants of "USA, USA" take over the crowd. The servicemembers are keeping people at bay -- and it looks mostly nonviolent -- but it's certainly not the moment of togetherness organizers were probably hoping for.

As you may know ... America's Independence Parade was canceled on Saturday due to the extreme weather. President Trump is supposed to speak at the event in about an hour -- but, as each minute creeps by, it's seeming less and less likely he'll take the stage.

Clearly, those who came from far and wide aren't happy about the change in plans ... and these proverbial fireworks are ready to explode.