When the National Oceanic and Atmospheric Administration (NOAA) indicates the northern lights may be visible across about 15 US states, it is signaling an elevated level of geomagnetic activity that can push auroral displays to unusually low latitudes. Such forecasts arise from disturbances in Earth’s magnetosphere, often tied to coronal mass ejections and high-speed solar wind streams, and they provide a rare opportunity for many regions to see auroral activity without traveling into polar areas. This evergreen explainer breaks down how these forecasts are created, where and when the aurora is most likely to appear, and how you can prepare to observe the display safely and effectively.
How NOAA Aurora Forecasts Work
NOAA’s Space Weather Prediction Center (SWPC) produces aurora forecasts by combining solar observations, satellite measurements, and physics-based models to estimate how Earth’s magnetosphere will respond to incoming solar wind and interplanetary magnetic field (IMF) conditions. Key inputs include solar flare data, coronal mass ejection (CME) timing and direction, and the orientation of the IMF’s southward or northward components. When the forecast indicates a high likelihood of geomagnetic storms, auroral oval models are used to estimate how far equatorward the auroral oval may expand, which in turn determines which regions can see displays. The result is a categorized outlook ranging from ‘slight’ to ‘extreme’ geomagnetic activity, each tied to probable auroral visibility ranges.
Primary Forecast Products
- 30-minute through 3-hour nowcasts that update in near real time based on solar wind measurements.
- 1- to 3-day outlooks that assess the probability of storms and the potential equatorward reach of the auroral oval.
- Impact scales that translate geomagnetic disturbance levels into likely effects on power grids, satellite operations, and navigation.
Which States Are Typically Included
Although the exact list shifts with each event, forecasts indicating visibility across about 15 states usually cover regions well beyond the traditional northern tier. In a typical strong storm scenario, the auroral oval may expand to include areas from the Upper Midwest through the Northeast and into the Appalachian and Pacific Northwest regions. The precise boundaries depend on the timing of the storm’s peak, local geomagnetic field characteristics, and cloud-free, dark skies. Places that commonly appear on such lists include parts of Washington, Oregon, Idaho, Montana, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan, Ohio, New York, Vermont, New Hampshire, Maine, and occasionally higher-elevation or more northerly sections of other states.
Representative Visibility Scenario
| Attribute | Verified Detail | Source Type |
|---|---|---|
| Approximate Number of States | About 15 states during strong storms | NOAA SWPC outlook products |
| Typical Geophysical Threshold | G2 (Moderate) to G3 (Strong) storms or stronger | NOAA Space Weather Scale |
| Key Forecast Horizon | 1–3 days for storm timing and extent | SWPC model guidance and consensus |
| Auroral Oval Expansion | Equatorward reach can extend into mid-latitudes | Ovation and other auroral oval models |
| Best Conditions | Dark, moonless skies with clear or partly cloudy conditions | Local weather forecasts and satellite cloud data |
When and Where to Look
For observers in the predicted states, timing is critical. Auroral activity is most common between 10 p.m. and 2 a.m. local time, though earlier or later displays can occur. Choose locations well away from significant light pollution, and favor northern horizons when possible, even if the lights appear low in the south or overhead. Check updated forecasts throughout the event window, because peak timing can shift by hours. If skies are cloudy, many observatories and local groups provide real-time sky cameras, and NOAA’s SWPC posts real-time data and imagery that can help you track progress.
Quick Preparation Checklist
- Monitor SWPC’s 30-minute and 3-hour updates in the hours before nightfall.
- Confirm local cloud cover and darkness using sky and weather apps.
- Dress for cold temperatures and allow 20–30 minutes for dark adaptation.
- Use red lighting on phones and flashlights to preserve night vision.
- Bring a simple tripod or steady support for phone or camera long exposures.
Camera and Photography Tips
Capturing the aurora requires balancing sensor sensitivity, shutter speed, and lens aperture. Modern smartphones with manual or night modes can sometimes record green or red hues when the display is held close to the eyepiece, but results vary widely. For interchangeable-lens cameras, start with a wide-angle focal length, a fast aperture (f/2.8 or wider), and a manual ISO range of 1600 to 6400, adjusting shutter speeds between 5 and 20 seconds to avoid star trailing at higher latitudes. Focus at infinity, use a remote release or timer to prevent shake, and bracket exposures if you are unsure. Review images on your camera’s histogram and avoid over-exposing highlights, which can clip detail in the aurora’s delicate structures.
Space Weather Context and Limitations
Aurora forecasts are inherently probabilistic and depend on conditions that can change rapidly. A modest shift in the timing or orientation of an incoming CME can alter how far equatorward the auroral oval reaches. Geomagnetic storms are categorized from G1 (minor) to G5 (extreme), and only moderate to strong storms (G2–G3 or higher) commonly expand visibility into the mid-latitudes implied by a 15-state forecast. Forecasters emphasize that even when the oval expands, cloud cover, local terrain, and skyglow remain decisive practical barriers. NOAA encourages the public to use forecasts for planning, while acknowledging that actual visibility is not guaranteed.
Related Phenomena and Safety Notes
Strong geomagnetic storms that make the aurora visible farther south can also induce electrical currents in long conductors and may affect satellite operations and power systems. Utility operators and grid managers often take precautionary measures during G3+ storms. For the public, the main risks involve travelling to dark sites in potentially wintry conditions and using equipment safely in cold weather. Prioritize road safety, dress in layers, and avoid areas with avalanche or ice hazards. Remember that forecasts are guidance, not certainty, and real-time confirmation from local observers or sky cameras can be more informative once conditions develop.
Staying Updated
To track auroral forecasts, consult NOAA’s SWPC official site for 30-minute through week-scale outlooks, kp indices, and model imagery. Many regional astronomy clubs and space weather apps provide concise summaries and push notifications for upcoming events. Dark-sky forecasts and cloud-cover models can be combined with SWPC’s outputs to choose optimal nights and locations. For ongoing learning, resources on magnetospheric physics, geomagnetic indices, and camera techniques help you interpret future predictions and improve your observations over time.