How a sea of clouds forms

Wake above the clouds and the valleys have turned to a white ocean, the peaks to islands. It happens on the calmest, clearest nights — and it’s more predictable than it looks.

On clear, calm nights, valley floors radiate their heat away and cool quickly. That cold, heavy air sinks and pools at the bottom, trapping moisture into a shallow layer of low cloud — while the peaks and ridges above stay clear, floating over a white ocean.

Why height matters

The trick is to be above the cloud layer but not so high you lose it. Viewpoints that sit just over the top of where the cold air settles tend to offer the best chance — close enough to look down on the sea, high enough to stay out of it. That margin between the cloud top and the peak is exactly what our model scores for each site.