Play was stopped with 4:51 left in the first quarter with Baltimore leading 10-0 when fans were ordered to seek cover.
Players stayed on the sideline for a few minutes before heading to the locker room as heavy rains and strong winds hit.
There were reports of at least one tornado touching down in Illinois and extensive damage in parts of the state. At Soldier Field, long lines formed in the upper deck as drenched fans tried to make their way toward the tunnel with lightning striking near the stadium.
RAVENS: General manager Ozzie Newsome remained in Chicago after Sunday’s game because he was not feeling well.
In a statement, the organization says the team doctor “recommended that Ozzie not fly tonight.” The extent of his illness was not clear.
SAINTS: Starting cornerback Jabari Greer hurt his left leg in the first quarter Sunday against the San Francisco 49ers and didn’t return to the game.
BILLS: Two men have been taken to a Buffalo hospital after one fell from the third deck of Ralph Wilson Stadium and landed on the other during the game against the New York Jets.
The injuries were not considered life-threatening.