The Northern Lights (Aurora Borealis) can be difficult to predict exactly, but when the Sun has had recent flare activity, seeing the Northern Lights is more likely.
On a night when the forecast is good for Northern Lights, the best viewing locations will be dark (i.e. little light pollution) and have a clear view of the northern horizon. If the aurora are active all night long, then viewing at midnight can be better than at other times, but going out when activity is high is the most important factor.
Auroral forecasts are given in Kp numbers, on a scale from 0 to 9. To have a chance of seeing the lights in PEI, the Kp level needs to be about 6 or above. These maps show where the lights will be visible for different Kp levels (the location must fall within the green band plotted on the map).
Various websites offer aurora forecasts (here’s one) or display the current “aurora oval”. There are also Twitter accounts like Aurora Alerts that tweet when the Aurora Borealis will be active and at what Kp level.