Outdoor tornado warning sirens' upkeep, trigger systems and, to some degree, testing patterns vary from municipality to municipality.

For the most part, however, there's one constant: Each municipality has a hard-and-fast plan, and is sure to keep those systems up to snuff.

Twin City Joint Fire Command Chief Gary Cook said the sirens in Sterling and Rock Falls are about 30 years old and are tested annually.

"We haven't seen one that is beyond repair," Cook said.

Unlike most municipalities, which test their sirens on the first Tuesday of the month, Sterling and Rock Falls test theirs once a week during tornado season, at 10 a.m. each Tuesday from March to November. From November to March – tornadoes' offseason, so to speak – the sirens are tested the first Tuesday of each month.

"We follow Illinois Emergency Management Agency guidelines," Cook said. "We like doing the weekly tests during the storm season."

Patti Thompson, who works in media relations for the IEMA, said a state statute requires municipalities to test sirens at 10 a.m. the first Tuesday of every month – and only at that time.

That said, she said there are no ramifications spelled out for municipalities that under- or over-test their systems, and she added that some might test a system that’s recently been serviced or repaired.

Around Whiteside County

Seth Janssen, Emergency Service Disaster Agency coordinator for Whiteside County, said the towns throughout the county control their own sirens – except Morrison, which is controlled by the ESDA.

In some areas, a dispatcher sets off the devices. In others, police and fire departments control the sirens.

The sirens are triggered by the click of a mouse in some cities. Officials in towns such as Albany or Fulton literally flip a switch to turn on sirens.

Click here to see a map of sirens within Sauk Valley Media's coverage area. A halo represents a siren's maximum range – 1 mile in any direction – but that range can be affected by myriad atmospheric conditions, such as wind velocity and direction, humidity, and precipitation.

In Whiteside County, sirens are triggered by National Weather Service's signal of a tornado warning, or if there is a tornado or funnel cloud reported by a trained spotter.

To constitute a severe thunderstorm, winds must be at least 70 mph, which is strong enough to blow trees down, or golf ball-sized hail must be reported.

"A severe thunderstorm is classified as a thunderstorm producing hail that is at least 1 inch in diameter or larger and wind gusts of 58 mph or greater," Janssen said. "As you can see, that differs from the criteria of sounding the siren. So, it's important to note that just because a siren isn't sounded, that doesn't mean dangerous weather is not a threat."

Lee County

In Ashton, the fire chief, assistant chief, mayor or police chief can set off the siren by dialing a phone number.

Conversely, in Harmon, the siren is triggered by a switch in a waterproof box mounted on the water tower. The sleepy town of about 120 will, however, start hearing a monthly test for the first time in July.

Most municipalities have their sirens serviced annually. Braniff Communications in suburban Chicago services the units in Dixon and Ashton and, if they need replacing, the company takes care of that, too.

A fifth siren is being added in Amboy at the fire station. The city uses a ready repair service to check each siren annually, and is working on getting a backup power supply for all of them.

Beyond upgrading equipment, however, sometimes what’s paramount is ironing out language to make sure sirens are used exactly as often as they should be.

For instance, about 2 years ago, Dixon added the word “straightline” to its prerequisite to blare its five sirens. Now the language reads that either a tornado must be spotted heading toward the city, or straightline winds that exceed 60 mph are incoming.

“There’s a balance to strike between not setting them off often enough and setting them off too often,” Police Chief Danny Langloss said.

He said the county is looking at streamlining its policy, to ensure residents aren’t over- or under-warned.

Carroll County

Earlier this month, the Lanark Fire Department installed a new tornado siren at the fire station. When there is an emergency, the siren will blow for 3 minutes straight. If damaging winds, hail or a funnel cloud are sighted by a weather spotter, the siren will sound for another 3 minutes. That is the requirement of a storm siren activation, fire Chief Randy Witt said.

Because the head of the siren rotates 360 degrees, it sounds like the siren is going up and down, he said.

There is a button at the fire department, and any of the staff members can sound the alarm with the direction of a weather spotter.

"The first staff member to get here or a staff member that is here sounds the alarm," Witt said.

There also was a new siren installed at Lake Carroll.

"We have been seeing increased population at the lake, and they also wanted to get a storm siren," Witt said. "We have it worked out to where when ours goes off, they set theirs off, too."

Both sirens were installed in the 1940s and because of that, Witt said, it was more than time for an upgrade. The sirens each carried a $20,000 price tag.

"They had money saved to purchase the siren, and we had money in miscellaneous funds," Witt said.

Gregory Miller, Emergency Service Disaster Agency coordinator for Carroll County, said the ages of its sirens vary.

"There are some in the county that are 20 years old, and there are some that are brand new," Miller said. "There are different ways to set them off, and it's really up to each town. The fire and police department each set them off."

Ogle County

The bulk of the sirens in Ogle County are owned by Exelon, "which graciously lets us use them," said Tom Richter, director of Ogle County’s Emergency Management Agency.

“Even though they should be treated as a secondary warning system, the sirens certainly played a very important role, and they’ll continue to play it,” he said.

Exelon provides the sirens within a 10-mile range of the Byron Nuclear Generating Plant, called the Emergency Protection Zone, which includes Oregon and Mount Morris. Exelon also owns and services the solo siren in Polo. When inclement weather rolls in, they're activated by the Ogle County Sheriff's Department. All the sirens have battery backup and are serviced and replaced, when necessary, by Exelon.

The sirens' primary use is for the Byron power plant, in the event of a nuclear-related emergency.

“I'm glad to say we’ve never had to use them for the nuclear facility for anything operational at the nuclear plant,” said Paul Dempsey, the plant's communications manager.

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COMING WEDNESDAY

One year after a tornado caused more than $2 million in damage, Woodhaven Lakes resort is alive and well, rebuilding, reforesting and tending to a record number of campers.