BATON ROUGE, La (LOCAL 33 AND FOX 44) – It has now been a year since tens of thousands of homes and businesses were under water in south Louisiana, but that flooding wasn’t caused by a tropical storm or hurricane.

Near-record moisture in the atmosphere and a slow-moving trigger to bring it down as rain caused the heavy rain to come down with few breaks starting August 11, 2016.

During the storm, the total amount of moisture in the air reached near-record levels, about 40 percent more than average for even typically humid August. That measurement is taken at the National Weather Service office in Slidelll, where Frank Revitte is the Warning Coordination Meteorologist. Revitte said, “We’re talking about an extreme amount of water, moisture in the atmosphere.”

All of that moisture just needed a trigger. It came in the form of a low pressure system moving slowly along the Gulf coast, taking nearly a week to move west from Florida through Louisiana.

Revitte said, “When your systems are moving that slowly, you have thunderstorms that are able to repeat continually over the same area.”

The National Hurricane Center monitored the system for possible tropical development in many of its morning outlooks. Its reports continued to state tropical development was unlikely due to the low’s proximity to land, but that it would produce heavy rain either way.

The system was never able to develop tropical characteristics and never produced strong enough winds to be considered a tropical storm.

The worst hit areas were from Lafayette to Baton Rouge, and then into Livingston Parish. The airport in Baton Rouge saw more than 17 inches in 3 days, while nearby cities picked up more than 2 feet or rain. This helped pushed the Amite River 5 feet above the old record level in Denham Springs set in 1983.

While the amount of rain seen in some cities was very rare, meteorologists say it doesn’t mean a similar storm can’t happen again this year or any other year.