The study, published on Thursday in the Journal of Geophysical Research - Atmospheres, found that tiny particulate matter from workweek pollution may "seed" summer clouds in the US Southeast, where plentiful hot, moist air tends to form more rain.

"There is a kind of a feedback loop," where pollution causes heavier storms during the workweek that flush smog from the atmosphere and tend to leave summer weekend weather clearer and less rainy, said Thomas Bell, an atmospheric scientist at NASA's Goddard Space Flight Center and the report's lead author.

"Pollution dies on the weekends, so you have the tendency for less severe storms and nicer, clearer air," he said.

On average, it rains more in the Southeast between Tuesday and Thursday than from Saturday through Monday, the NASA-funded study found.

Its satellite data found that afternoon rainfall peaks on Tuesday, with 1.8 times more rainfall than on Saturday, which experiences the least amount of afternoon rain.

The pollution-rain connection was less pronounced in western half of the country, where it tends to be drier in the summer.

In cloud seeding, water and ice in clouds grab hold around particles, forming additional water droplets that lead to heavier rainstorms.