GRAND RAPIDS, Mich. (WOOD) — The aurora borealis is one of the most beautiful and one of the most difficult things to predict on the planet. Those lucky enough to catch it typically burn it into their memories for years to come. One viewer wants to know, what is the best way to know when the northern lights will be visible?

Check forecasting sites

There are several forecasting sites for the northern lights. One of the best is the University of Alaska’s Geophysical Institute. This site monitors the current aurora activity, as well as projects forward for the next month or so what the likely aurora forecast will be.

When looking at aurora forecasts, remember that the accuracy level is only moderate to low. Aurora forecasts frequently fail. Still, they are a great place to start. Often times they are made based on coronal mass ejections emitted from the surface of the sun. Often the timing changes, or the intensity. Both can drastically impact what we see here on Earth.

Maps are often released showing the likely placement of an aurora. In these forecasts, the shaded green area shows the most likely places the aurora would be directly overhead.

The green line, and north, are areas that have a chance of seeing the aurora far on the northern horizon.

Courtesy University of Alaska

Look for a high KP Index

When checking forecasting sites, look for time frames where the KP Index looks high. The higher the KP Index, the further south in latitude an aurora will be able to reach.

Here is a good guide showing how far south the aurora can reach for a given KP Index value is in the United States.

Usually a KP Index of 5 more more allows the Upper Peninsula of Michigan to see the northern lights. A KP Index of 6 or 7 usually allows a faint green glow to appear in the skies of the Lower Peninsula.

Keep an eye on the more predictable factors

The best aurora displays are often reliant on other factors besides just space weather. Be sure to check things like the local forecast and the current moon phase before planning a trip to see the northern lights. Auroras are formed when charged particles from the sun slam against our outer atmosphere. These charged particles excite electrons and atoms in the outer fringe of our atmosphere, releasing waves of light.

If there is a cloud deck forecast during an auroral show it could block the display completely. A bright moon phase could reduce the intensity of a show.

Be sure to pick a place to watch the aurora that is far from city lights and watch the news and space weather sites for tips on when the auora might be peaked due to a solar storm.