Plano's emergency sirens went off about 11 p.m. Wednesday for about 20 seconds -- enough time to wake some people and cause panic.
The Plano Emergency Management director said the sirens going off was human error -- someone in her office saw a thunderstorm warning and sounded the sirens.
"Because we have had so many high profile storms in a short amount of time, people have heard the siren sound frequently. So even though we only had a short duration for the sirens, the fact that they were sounding at all has people on edge," said Carrie Little, Plano Emergency Management Director.
Cities can set their own guidelines for sounding the alarms. The City of Plano turns on the sirens when winds reach 73 MPH, hail is larger than a half-dollar or there's a tornado warning.
The sirens are meant to warn people who are outside at the time of a storm to seek shelter. Little said it's an added bonus if people can hear the sirens inside their home.