Photoperiod-based sleuthing

From Super-Fun Geography Studies with Journey North's Mystery Class (Melissa Wiley, The Lilting House, January 24, 2007):

As one of my little ones used to say, I'm so a-cited! It's almost time to begin a new season of happy hunting with the Journey North Mystery Class. Ten classes of schoolchildren around the world have been chosen to be Mystery Classes, and it's up to the rest of us to track down their location. You too can join in the fun!

Here's how it works...