Whatever the cause, snowy owl irruptions into temperate zones delight birders. Snowy owls are difficult to miss. Unlike most owls, they are active by day and thus easily seen. Furthermore, they prefer open habitat -- pastures, hayfields, airports, golf courses, beaches, cemeteries, etc. -- and this also makes them easy to see. Often they perch conspicuously on large rocks, fence posts, power line poles, and even the roofs of buildings.
Snowy owls stand about two feet tall, have a wingspan of more than four feet, and weigh about four pounds. Older males are mostly white; first year birds are heavily marked with black bars, and adult females show some black barring. Often during these periodic southward irruptions, many birds are juveniles. This suggests that when food becomes limiting, young birds are the first ones to leave the far north.
To learn if any snowy owls have been seen near you, call a local nature center or wild bird store. Or search online for "snowy owls near ______" and fill in your location.
If you get lucky and find a snowy owl, keep your distance. These birds are stressed, hungry, and have traveled a long distance. If you get too close and spook them, you only compound the stress.
Sometimes when searching intently for a special bird, eyes can deceive. Beware that sometimes all is not as it seems. Every birder has been duped a time of two (or 20) into thinking a prominent rock, stick, or plastic bag is a bird. I've got several "leaf birds" on my life list. There's no shame in being fooled. To see what I mean, visit this website by Matt Webb: http://thatsnotasnowyowl.tumblr.com.
For continuing coverage of the snowy owl invasion, visit www.ebird.net.