All across the Twin Cities on Monday, people were checking their shoes, wondering if they’d stepped in something.

Because everyone smelled — let’s just say it — poop.

But the odor wafting through the air wasn’t caused by our furry friends. It came from our farming friends.

This is the time of year when farmers fertilize fields, usually with anhydrous ammonia or plain old manure. And fall’s variable temps can unleash the beastly smells.

“What happens [is], the temperatures dip below freezing and lock in the good stuff, and then if it thaws, the odors and nitrates are released,” said Daniel Dix, a meteorologist with the Minnesota Pollution Control Agency.

The smell spread not just through Minneapolis and St. Paul, but all through the metro area, he said — and undoubtedly was noticed throughout rural Minnesota, Iowa and Wisconsin, where residents are probably more accustomed to it.

In this file photo, hog manure is spread over grain fields near Redwood Falls for fertilizer, as Rick Serbus headed toward his tanker truck for another load. Thawed fertilizer was responsible for the stench around the Twin Cities and the state Monday.

“Welcome to Minnesota,” Dix said.