Interpreting the Aurora
The auroral activity forecast predicts the expected location of the most active auroral forms that can be expected for the given period. Aurora viewing is also affected by a variety of other factors, such as cloud cover, moonlight and urban light pollution, so what you see will be strongly affected by your particular location and meteorological luck.
The best time to observe aurora is near local midnight, when the most active forms often occur. More precisely, the time to shoot for is an hour or two prior to local geomagnetic midnight, and the forecast maps found here are calculated for that time. If you are a serious aurora watcher, plan to spend the night from about 9 p.m. to 3 a.m. watching for auroral action.
Auroral activity tends to come in waves during the evening, which are called auroral substorms. Even during an active period, there will be lulls in which the auroral activity is subdued; however, the patient observer will often see a new burst of activity within an hour or two.
The auroral forecasts categorize auroral activity as follows: