People in neighborhoods all across central Iowa heard tornado sirens Sunday night, but those sirens don't necessarily mean there is a tornado in the area.
Wind speeds of more than 70 mph can trigger the sirens too.
Each county decides when the sirens should go off.
Polk County Emergency Management’s A.J. Mumm says there's no harm in over warning residents. “It`s a balancing game between over warning and under warning and if we get people the information they can make the best decision for them and their family.”
The sirens are primarily used to alert those who are outside to seek shelter indoors.
Polk County Emergency Management sounded 97 of its 130 sirens on Sunday.