The sky fell Monday. Literally. Billions of gallons of rain fell on San Diego

As much rain fell in just six hours Monday as does normally in three months.

Sound like a lot? So, how much precipitation did San Diego get that day? An astonishing 2.73 inches, when we normally get about 2 inches on average for the entire month of January. It was the city's rainiest day ever in January, according to records dating to 1850. Of course, Monday was merely the final insult in three days of rain, beginning on Saturday.

A rough calculation shows that more than 150 billion gallons of water fell on San Diego County over three days, much of it in a three-to-six-hour period, Ryan Maue, former chief scientist for the National Oceanic and Atmospheric Administration, said in an email to The Associated Press. He said the city’s drainage canals and infrastructure are not able to handle such a deluge.

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“The rainfall rates and duration ... overwhelmed the capability of the urban and natural interface to reroute the water back to the ocean especially with so much also falling inland at high elevations,” Maue said.

It was the fourth-wettest day on record in the entire history of San Diego weather measurements, according to the National Weather Service.

San Diego has gotten more rain over the past three days, than during the past three months combined. In fact, the three-day total is nearly double the past three months.

Before the storm, rainfall forecasts had predicted 1 inch on the coast and double that in the mountains.

The unprecedented flooding and damage prompted states of emergencies across the county.