Doyle Rice, USA TODAY

The massive amount of rain that caused the devastating flooding in the past few weeks in Missouri was a rare 1-in-1,000-year event, meteorologists said Friday.

Most of the “once-in-a-millennium” rainfall from late April to early May occurred in Texas and Howell counties in southern Missouri, the National Oceanic and Atmospheric Administration said. Some areas picked up over a foot of rain within a few hours April 29.

"This incredible rainfall resulted in widespread and historic flooding," the National Weather Service in Springfield, Mo., said. "Numerous roads, bridges and buildings were destroyed."

Other portions of the state, as well as parts of Illinois and Indiana, experienced less extreme rainfall, on the order of 1-in-200 and 1-in-500-year levels.

A 1-in-1,000-year rain event is a statistical way of expressing the probability of such a massive rainfall occurring in any given year in a specific location, according to the National Center for Environmental Information, which is part of NOAA.

And, it's the extreme rainfall amount in such a short amount of time that's the 1-in-1,000 year event, not the resulting floods, NOAA hydrologist Sanja Perica said.

This is at least the 10th "1-in-1,000" year rain event across the U.S. since 2010.

While it's not yet known if climate change is to blame for each individual extreme rain event, heavy downpours are increasing nationally, especially over the past three to five decades, with the largest increases in the Midwest and Northeast, according to the National Climate Assessment, a federal document released in 2014.

That means we're more likely to see 1-in-1,000-year rains as the planet warms, the Weather Channel said.