When Tropical Storm Allison suddenly formed 80 miles off the coast of Galveston, Texas, on Tuesday, June 5, 2001, no one expected that, five days later, it would go on record as one of the most devastating rain events in the history of the United States. Neither historical data nor weather forecasts could adequately predict this extraordinary storm that, before leaving Texas, would dump as much as 80 percent of the area's average annual rainfall over some Houston and Harris County neighborhoods, simultaneously affecting more than 2 million people. When the local rains finally eased, Allison had left Harris County, Texas, with 22 fatalities, 95,000 damaged automobiles and trucks, 73,000 damaged residences, 30,000 stranded residents in shelters, and over $5 billion in property damage in its wake. Simply put, everything about Allison was "off-the-charts."

One thing everyone in our area learned, without qualification, is that it does not take a "perfect storm" to be a perfect flood maker. Allison's slow and erratic progress - first moving inland to the north, then meandering back to the Gulf of Mexico - combined for a horrific one-two punch that dealt many localities in the Houston region a critical blow. After flooding about 1,000 residences during its initial pass through the area June 5-7, Allison returned June 8-9 to deliver its knockout shot. At one point during this second pass, 28 inches of rain fell during a 12-hour period just northeast of downtown Houston. Such incredibly intense cloudbursts over heavily populated areas set Allison apart from every storm to hit Texas in the past century.

Originally a mere "disturbance" passing through the Yucatan Peninsula into the Gulf of Mexico, Tropical Storm Allison formed Tuesday, June 5th, 80 miles off the Southeast Texas coastline. That night, it made landfall west of Galveston, with sustained winds of 48 miles per hour. Remaining over Harris County initially for four hours, it dumped as much as 12 inches of rain and flooded some 800 residences as it drifted slowly to the north. During the next day, Allison would continue its inland track and eventually reach Lufkin on Thursday morning, where it appeared to weaken and stall. Even then, when the storm appeared to be moving away from Harris County, it still produced enough rainfall locally on Thursday the 7th to flood an additional 200 area residences.

Unexpectedly, Allison looped back to the southwest - drawing new moisture off the Gulf and re-intensifying. The heavy rains, both on Tuesday evening and Thursday morning, had saturated the ground, which caused immediate, excessive runoff when Allison returned to deliver the knockout punch Friday night and early Saturday morning. Friday night, as much as 28 inches of rain had fallen in parts of the county - flooding thousands of residences, stranding thousands of cars on hundreds of roads, and prompting Governor Perry and President Bush to declare Harris County a disaster area. On Saturday alone, units of the Coast Guard, the National Guard, and local emergency agencies rescued nearly 7,000 people. In addition to these documented rescues, individual citizens acting on their own rescued thousands of other flood victims. Monday night, some 30,000 Houston area residents sought refuge in 51 shelters countywide.

Leaving Texas, Allison produced rainfall amounts ranging from 20 to almost 30 inches over parts of southeastern Louisiana. The storm also brought heavy rains across the northern Gulf Coast, with amounts of 10 to 12 inches from Gulfport, Mississippi to Tallahassee, Florida. Areas of North Carolina received as many as 21 inches of rain while southeastern Pennsylvania recorded amounts of eight to ten inches - capping nearly two weeks of devastation.