Monday morning’s deluge in Washington was exceptional in its intensity and for the amount of water it dispensed in a short time.

In just an hour, about a month’s worth of rain drowned the District of Columbia, a staggering 3.3 inches falling at Reagan National Airport between 9 and 10 a.m.

The first-ever flash flood emergency was declared for the city and nearby Virginia locales Arlington and Alexandria, which suffered damaging inundation.

The severity of the precipitation over such a short span had about half of 1% chance of happening in any given year.

Three billion gallons came down in D.C. proper.

(If including all of Virginia and Maryland in this calculation, the volume balloons to nearly half a trillion gallons, according to meteorologist Ryan Maue, who ran a similar analysis. Meteorologist Ryan Miller estimated that more than a billion gallons fell in Arlington.)

How much water is 3 billion gallons?

That sum of water would be enough to fill 27 million standard hot tubs. It could also fill 1.1 million hot air balloons. All that water could also fill the White House — floor to ceiling — 103 times.

All the water that hit D.C. on Monday would weigh the equivalent of 102 million President Donald Trumps. Stacked end on end, that would be enough 45th Presidents to stretch 120,000 miles — halfway to the moon.

If the rainfall were distributed equally across everyone living in D.C., each person would receive 35,000 pounds of it, roughly as much as goes into a residential swimming pool.

That amount of water could sustain half the world’s population for a day.