Following a few days of rare solar activity, the National Oceanic and Atmospheric Agency (NOAA) has issued a Severe (G4) Geomagnetic Storm Watch for this weekend. In addition to potential disruptions of the electric power grid, navigation, radio, and satellite operations, NOAA experts predicts that because of the storm, the Northern Lights may be visible in much of the United States, “as far south as Alabama and Northern California.”

Here’s what to know about catching a glimpse of the Aurora Borealis this weekend, and the other potential impacts of a geomagnetic storm.

What is a geomagnetic storm?

Before getting into the Northern Lights, let’s talk about the potential geomagnetic storm that could cause them. According to Shawn Dahl, a service coordinator at NOAA’s Space Weather Prediction Center (SWPC), two sunspot clusters—one in the northern hemisphere and one in the southern hemisphere—have been sending out a large number of solar flares of high-energy radiation this week.

Currently, the SWPC is monitoring at least seven coronal mass ejections (CMEs)—explosions of plasma and magnetic fields from the sun’s corona that can cause geomagnetic storms when they’re directed at Earth. This is what prompted the agency to issue a Severe (G4) Geomagnetic Storm Watch for the first time since January 2005.

“We have a rare event on our hands,” Dahl said during a press briefing call Friday morning. “Yeah, we’re a little concerned. We haven’t seen this in such a long time that we thought it warranted special attention.”

What happens during a geomagnetic storm?

According to NOAA, geomagnetic storms can impact Earth in two major ways:

Visibility of the Northern Lights extending much farther south than usual, and

Potential infrastructure disruptions, including to the electric power grid, communications, navigation, radio, and satellite operations.

What time will the geomagnetic storm occur?

While the SWPC has “a high confidence” that CMEs are heading towards Earth, “we’re less certain on the timing of these events,” Dahl says. Right now, the agency predicts that the first CMEs could reach Earth as early as this afternoon Eastern Daylight Time, and continue into the evening. It’s also possible that additional solar eruptions could prompt the geomagnetic storm watch to be extended through the weekend.

We’ll have a much better idea of the timing of the potential geomagnetic storm when the CMEs reach a point roughly one million miles from Earth, where NASA and NOAA satellites monitoring solar wind conditions are positioned.

“That’s when we will know the intensity, and what may develop here at Earth,” Dahl says. “That’s we’ll have more certainty and begin to issue warnings.” The CMEs travel at a speed of around 800 kilometers per second, so when they pass the satellite, “there could be about 20 minutes or 45 minutes of lead time” before they reach Earth, he says.

The SWPC has notified the National Grid and other operators of infrastructure systems of the predicted geomagnetic storm, “so they are able and prepared to take mitigation efforts as much as possible throughout this event, if it should unfold to the levels that we currently are anticipating,” Dahl says.

How and where to see the Northern Lights

Geomagnetic storms do more than potentially disrupt the infrastructure: They can also trigger displays of aurora that extend far beyond their usual geographical reach. If this weekend’s forecasted geomagnetic storm is severe enough, NOAA experts predict that the Northern Lights should be visible over much of the northern half of the country, and potentially as far south as Alabama and Northern California. Because the aurora oval doesn’t extend across North America evenly, those in the midwest and northeast “are always a little more likely to see an aurora further south than somebody much further to the west at the same latitude,” Dahl says.

As usual, for the best chances of seeing the aurora—and most celestial activity, for that matter—head to the darkest skies near you. But first check the weather forecast: Any type of precipitation or cloud cover may obscure views of the natural wonder.

When will the Northern Lights be visible?

Until the first CMEs begin to pass the satellite one million miles away, Dahl says it’ll be difficult to predict precisely when and the Northern Lights may be visible in the United States. For now, NOAA forecasts that the aurora display will likely peak late Friday night, but could continue into Saturday.

How to prepare for geomagnetic storms

Given the potential for disruptions to the power grid and other infrastructure, Dahl says that you can prepare for a potential geomagnetic storm the same way you would for any other power outage. “Everybody should always have a plan, batteries, weather radio, [and] perhaps a generator, depending where you live in the country, and how prone you are to normal power outages,” he says. “They don’t need to do anything extraordinary if they’ve already got these measures taken care of, because [geomagnetic storms of the predicted severity] are very rare.”

You can track the geomagnetic storm yourself on the SWPC website, which be updated with new information as it happens, or subscribe to receive NOAA space weather alerts, warnings, and watch information.