A foul smell wafting across the Twin Cities this week is the result of changing weather and common fall farming practices.
After soil temperatures cool below 50 degrees, farmers inject animal manure and anhydrous ammonia into the soil.
This year, temps dipped below freezing and then warmed up again, releasing some odor from the nitrogen that was put in the soil, said Minnesota Pollution Control Agency meteorologist Daniel Dix.
A cold front from the northwest helped clear the air Monday night. But the smell could come back later this week.
"We're looking at Thanksgiving into Friday, the winds will switch out of the south again and we could have more of that especially as the temperatures warm back into the 40s and even the 50s. So it may happen again until another cold front comes through on Saturday and cleans it out again," Dix said.
The fall smell is common in rural parts of the state, Dix said, but happens less often in the Twin Cities.
"I lived in Mankato, so I grew up used to it. I think people here in the Twin Cities metro, they don't expect that or think that it happens, but we are in the middle of a large farming area, so it does happen," said Dix, who adds there are no health concerns with the foul odor.