Visitors can expect to encounter fog or a fog ocean on the mountaintop once or twice a week in summer, and two or three times a month in winter.

To a large extent, the mountain ridge causes fog.

Moving air masses must rise to get over the mountain.  As the air rises, it expands and cools.

If the air is moist, cooling may cause moisture to precipitate as tiny droplets, and produce the clouds that we call fog.

Sometimes, an atmospheric inversion may produce a strange effect: fog lies like a soft white blanket on the Shenandoah Valley and the Piedmont, while the mountaintop is clear.

If conditions are right, you can look down on a “fog ocean,” with the lower peaks rising above it like islands.

Information on this unusual weather phenomenon comes from Shenandoah National Park and The Guide to Shenandoah National Park, by Henry Heatwole.  If you would like to learn more about seasonal climate changes and weather conditions in the park, learn more here.