In case you wound up here from Reddit being the steaming pile of shit that it is: deleting proper discussion due to the upcoming Blue Angels - you aren't crazy, and there were three explosions today in First Hill.
I don't know what they were from, and all reddit threads the noted it were deleted, even though the Blue Angels aren't doing practice until tomorrow, and morons in the city have already lost their minds coining legit concerns on people being "Whiny."
There were three percussive blasts, and though I lost track of time, while the sun was up and past 4( for the first at least?)pm. There were no jet noises, and it sounded like a contained explosion - like an explosion in a trash can. The first explosion caught me off guard, and the second two were closer together.