The thick fog in the forest in the early morning is caused by a phenomenon known as radiation fog. Radiation fog occurs when the ground loses heat due to radiation on a clear, calm night, causing the air in contact with the ground to rapidly cool. As the air cools, its moisture condenses into droplets of water, forming the thick fog we see.

In a forest, trees and vegetation help keep cool air close to the ground, creating ideal conditions for radiation fog to form. In addition, moisture released by plants during transpiration can increase air humidity, increasing the likelihood of fog formation.

In general, the principle behind the formation of dense fog in the forest in the early morning is the cooling of the air near the ground, which leads to condensation and the formation of fog.