Northern Lights Forecast: 20 States May See Aurora Saturday Night - Forbes

The northern lights may be visible overnight from up to 20 northern U.S. states on Saturday, April 18, into Sunday, April 19, according to a forecast by space weather experts at the National Oceanic and Atmospheric Administration. The forecast is for a G1 or G2 geomagnetic storm, which could see aurora on the northern horizon from U.S. states.

With a new moon on April 17, the timing is perfect for dark skies. It comes just as Comet C/2025 R3 (Pan-STARRS) makes its final appearance in the pre-dawn night sky.

Northern Lights Tonight: Where And When

A G1 or G2-class geomagnetic storm could see aurora visible on the northern horizon from around 10 northern U.S. states and Canada. U.S. states with the best chance include Alaska and (northerly parts of) Washington, Idaho, Montana, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan and Maine. If a G2 geomagnetic storm develops — which is briefly predicted for early evening in North America time zones — states farther south may also see aurora, including Oregon, Wyoming, Nebraska, Iowa, Illinois, Indiana, Ohio, New York, Vermont and New Hampshire.

To check visibility in real time, use NOAA’s 30-minute aurora forecast or download apps such as Aurora Now, My Aurora Forecast or Glendale Aurora for up-to-the-minute alerts and live solar wind data.

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Northern Lights Alert: Coronal Hole

The northern lights are caused by the solar wind, a constant stream of charged particles flowing from the sun that interacts with Earth’s magnetic field. While most are deflected, some particles spiral along magnetic field lines toward the poles, colliding with oxygen and nitrogen atoms high in the atmosphere. These collisions excite the gases, causing them to release energy as shimmering light.

In this case, the solar wind is made more potent by a high-speed blast of solar wind coming from a hole in the sun’s corona (its outer atmosphere).

Northern Lights Tonight: Forecast

“G1-G2 (Minor-Moderate) geomagnetic storming levels are expected on April 18 as negative polarity CH HSS geomagnetic conditions persist,” stated NOAA, referring to the coronal holes' high-speed stream of solar wind. “Active to G1 (Minor) levels are expected to continue through April 19, followed by unsettled to active conditions on April 20, as HSS effects linger.”

That negative polarity is crucially important. Aurora-chasers frequently use the Kp index to predict the intensity of a geomagnetic storm. Still, for aurora displays, the interplanetary magnetic field’s Bz component is more important (you’ll find it in some of the above apps and on SpaceWeatherLive.com). Bz determines how easily solar energy enters Earth’s magnetosphere. When Bz points north (positive), Earth’s field resists it; when Bz swings south (negative), the two fields connect, allowing plasma to stream in. A sustained southward Bz of −5 nT or stronger usually signals an imminent display of aurora.

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Northern Lights Forecast: How To Photograph Aurora

The new moon makes this potentially a great opportunity to capture long-exposure aurora photography on the northern horizon. A mirrorless or DSLR camera is ideal (ISO 1600, 2-10 seconds, f2.8), though newer smartphones are increasingly capable of stunning results. If your smartphone has a Night Mode or Pro Mode, you can capture a beautiful aurora photo with these steps:

Use your main lens, not the ultra-wide, for sharper results.
Stabilize the camera using a tripod or rest it on a firm surface such as a car roof, wall, or post.
Shoot in RAW format if available, as it makes post-editing easier.
Expect long exposures between five and ten seconds. Even faint glows that look grayish to the eye often appear vividly green, purple or red in photos.

Wishing you clear skies and wide eyes.