Rainfall gauges overflowed. Crop fields flooded. Streets submerged.
Sunday nearly made the record books for the most rainfall in a 24-hour period locally. Hours of heavy pouring cumulated to 6.36 inches in McLean County, 5.48 inches in Muhlenberg County and 4.39 inches of rain in Ohio County, according to Kentucky Mesonet data.
In Owensboro, the official precipitation count is unknown. The city’s weather station from the National Weather Service in Paducah was not functioning on Sunday.
“These past few days, the gauge had been acting up,” said NWS meteorologist Andy Lesage, who wasn’t sure when the gauge will be fixed.
But Owensboro just might have broken its observed daily rain record of 5.51 inches from March 31, 1993. A volunteer observer from the Community Collaborative Rain, Hail and Snow Network reported 5.5 inches of rainfall about five miles south of Owensboro.
“Storms were following each other hour after hour,” Lesage said, with an inch-plus of rain descending during each consecutive hour. “The totals were reading near-record levels.”
Flash flooding at that rate isn’t common. Five inches of rain over a 24-hour period might occur every one to two decades, and McLean’s total of 6.36 inches would be expected about once every 50 years, according to Stuart Foster, state climatologist and director of the Kentucky Mesonet.
The timing did prove helpful for local air quality. Before the rain, dust traveling from Africa worsened air pollution across the nation. The Saharan Air Layer, a mass of dry, dusty air that forms over the Sahara Desert, remains active during the summer months and sent an unusually large outbreak across the Atlantic last week, according to the National Oceanic and Atmospheric Administration.
Particle pollution from dust can cause nose, throat and eye irritation shortly after exposure and negatively impact health. Individuals with asthma, chronic obstructive pulmonary disease or even COVID-19 face higher risks for complications.
Heavy rain usually reduces pollution. Raindrops attract aerosol particles before hitting the ground in a process called coagulation. This can help reduce particulate matter — especially larger particulates — and help wash away dissolvable pollutants.
Air quality was considered the lower end of moderate in Owensboro Monday afternoon, according to AirNow, a national database for air quality.
“Any dust in the area would have been rained out,” Lesage said.
There will be additional rain and a lower probability for air quality impacts this week. A second, milder plume of dust from the Sahara is expected to reach the Gulf of Mexico by mid-week.
NWS radars show potentially heavy rainfall this week beginning Monday night or early Tuesday.