Until it really works, you can't help wondering how well it's going to operate. So Chris Weldon was relieved by what happened at 3:38 p.m. one Saturday this month.

At 3:37, the National Weather Service issued a winter storm warning. Within 30 seconds, a new mass-alert system called CodeRED buzzed Weldon a warning that the storm was bearing down on him.

"At first I'm like 'Holy Hannah, what's going on!?' " said Scott County's emergency management director. "But I was impressed. The speed of that second alert means every citizen is capable of finding out what's going on almost simultaneously with me -- and well before they'd likely hear from the media or other sources."

It has taken the county and its cities quite a while to get such a system rolling.

Neighboring Dakota County, using a different vendor, has had one since 2009. And CodeRED's Florida-based developer reports that 30 Minnesota counties already are using it, along with a host of other public users, spinning out 1 million messages within the state during the past year.

But now the county is gearing up for a full public launch. And there are some things you should know about becoming fully connected to it -- or, perhaps, disconnected from it, if the thought of a 2 a.m. phone call about flash-flood warnings does not appeal to you.

If you have such reservations, the chairman of the Scott County Board agrees with you.

"I do not want to have to hear about every thunderstorm that's coming," sighed Tom Wolf.

Prior Lake's city manager, Frank Boyles, grimaced when told that jurisdictions have been known to use the system for neighborhood alerts concerning lost cats.

"I'd like to see it used for more than just major emergencies," he said, "but you have to strike a balance."

What it does

CodeRED allows for at least two things that are hard to achieve any other way.

The first is real-time alerts that blanket a whole area and even reach commuters at work in a distant spot if the system has been provided their cellphone numbers and e-mail addresses.

The second is precise targeting so that storm warnings, for instance -- an option folks can decline -- can reach only the parts of a county a weather system is actually expected to strike.

Weird things are going to happen with that, Weldon cautioned, including the fact that people "on one side of a street are going to hear things that people right across the same street are not. Every alert will have its own boundaries. It has to stop somewhere."

But the potential also exists for a whole part of town, for example, not just folks within 500 feet, to be alerted to a public hearing on a proposed project.

Not everything needs to be a phone call. Officials can hit the accelerator when it's urgent and catastrophic, such as a known tornado, while backing off and sending less intrusive alerts when it's something like a sex offender moving into the neighborhood.

If you're curious about what kinds of alerts go out, you can download CodeRED's app onto a mobile device and it will give you a map of the nation, highlighting all manner of alerts being issued at that moment. There are still, for instance, alerts going out on the East Coast in the wake of Hurricane Sandy, inviting people to follow-up events.

In fact, Sandy is one big touchstone these days for companies offering this service.

The Sandy test

Last week, a firm called Everbridge, used by Dakota County, held a Web-based forum for potential customers across the nation during which the presenter suggested 10 questions to competitors like CodeRED that might "make them sweat." One of them was how well they did with Sandy.

Stephanie Meyers, spokeswoman for Emergency Communications Network, which developed CodeRED, said the answer is: Smoothly.

"We did 15 million calls during Sandy over multiple days," she said, "and a ton of texts and e-mails. The calls are important because there are a lot of power outages still. And 100 percent of our database was contacted with critical information: evacuation orders, curfews, where to get water and food, that type of thing. It's very time sensitive."

The types of situations that could lead to mass alerts in Scott County, Weldon said, include "missing kids or vulnerable adults, evacuations, imminent threats to public safety or health, wildfires, road closures, utility outages, water main breaks, tornados, flash floods or thunderstorm warnings."

All businesses are being asked to register. Among residents, the system likely has your land-line number, but those being sought out in particular to visit the county's website and sign up include people with unlisted phone numbers, those who have changed a phone number or address within a year, or those who use a cell or VoIP phone as primary point of contact.

A key thing to know, Weldon said, is that in late December or early January a test call will go out to all those whose numbers are in the database. The date of that call will be publicized through the media, and that will be the way for folks to know whether they're connected.

The system is "only as good as the numbers entered in," Weldon said. "For weather alerts only, there's an opt-in option. Some people won't want those calls to wake them up, or they have weather radio already, or they like their cellphone service that does that for them."

The delay in the system's reaching Scott County, officials say, had partly to do with the desire to have all the cities and the county join the same system. There was also a pause while Scott considered whether to merge emergency communications with Carver County.

"We didn't want to buy something, then consolidate," Weldon said. "There's always budget considerations, as well. And we needed to talk to multiple vendors. It's a process."

David Peterson • 952-746-3285