Every year, early-morning hikers reaching the Blue Mountain Peak summit photograph crystalline white fields and declare online that it snowed. What they are actually witnessing is classic frost formation. The distinction between frost and snow is structural, rooted in where the water vapor phase transition occurs.
Snow originates high within the cloud deck. Ice crystals form via deposition, agglomerating into delicate dendrites that drift through sub-freezing air columns to carpet the forest floor. In Jamaica, the clouds overhead are perpetually above 32°F (0°C). Snow never falls out of them.
Frost, by contrast, develops strictly at the ground boundary. On calm, cloudless winter nights between late December and mid-February, high elevations experience intense terrestrial radiational cooling. Thermal energy escapes unhindered into the dry upper atmosphere. The ground surface, alongside grass blades, mosses, and wooden shelter railings, cools much faster than the surrounding ambient air.
When the surface temperature plunges to the freezing point, dew drops freeze into tiny beads, or ambient water vapor deposits directly onto leaves as hoarfrost. According to field logs recorded across decades by the Jamaica Meteorological Service and park rangers at the Blue and John Crow Mountains National Park, this phenomenon coats entire swaths of the peak in brilliant white. It looks remarkably like light snow dusting. Up close, however, it is entirely bonded to vegetation, lacking any aloft precipitation structure.
