He was awake and alert at the North Alabama Medical Center but had suffered burns, the Florence Police Department said.
It happened at the intersection of Chisholm and Gresham roads, the department said in a statement, and other officers who were present immediately rendered aid.
They had been in the area deploying barricades amid a flash flood warning expected to expire at 5:45 p.m. CDT, authorities said.
The National Weather Service had warned of an extraordinary chance of severe weather in the area for the day.
“To put this into perspective, we haven’t had a ‘High Risk’ day in Northern Alabama since April 28, 2014,” the Weather Service’s Huntsville office tweeted early Thursday morning. “We are expecting destructive winds, strong tornadoes, large hail, and flash flooding across our entire area, despite the location of the ‘High Risk.’”
The risk remained in place Thursday evening, authorities said around 4 p.m.
A tornado warning has since been lifted, but forecasters said they were still possible into the evening across all of northern Alabama and southern middle Tennessee.
Authorities reported major tornado damage around Birmingham, where photos showed downed trees and decimated homes and businesses.
Lauderdale County was under a tornado watch until 8 p.m.
“Please do not let your guard down,” the Weather Service tweeted. “Just because you have not seen severe weather yet, or that it is raining now, does not mean you are out of the woods. We are just now starting the marathon that will be this afternoon and evening.”