I spend a lot of time looking for this kind of phenomenon (bit of a hobby), Thork, get out more, sundogs and many other types of halo are observable at least on a weekly basis towards sunset on a clear day, sometimes there are halos, arcs & sundogs, the colder the better but even in summer the upper atmosphere is easily low enough in temperature to produce them. As to how, the best site I found is
http://www.atoptics.co.uk/halosim.htm , there are about ten easily understood pages of explanations and photos of histories, how why and when, or you can skip straight to the sundog bit, either way it's a good site.
It even has a halo simulator
http://www.atoptics.co.uk/halo/halfeat.htm showing how it all works, with mathematical models of the ice crystals.