Final answer:
As humidity increases, snow crystals become more symmetrical due to decreased evaporation rates. These conditions allow snowflakes to maintain their intrinsic crystal structure and develop evenly.
Step-by-step explanation:
As humidity increases, snow crystals that are growing tend to become more symmetrical. Increased humidity means that the air has a higher concentration of water vapor, reducing the evaporation rate of the snow, as there is a decreased difference in water vapor pressure between the snowflake surface and the surrounding air (increasing humidity leads to reduced evaporation rates due to decreased difference in water vapor pressure). This allows the snowflakes to retain their intricate crystal structure and develop more symmetrical shapes. On the contrary, in drier conditions, the evaporation rate is higher, which can lead to less symmetrical snowflake growth. Additionally, the specific phase diagram for water highlights that snow is a solid phase of water formed from ice crystals. When environmental conditions, like humidity, are right, moisture is absorbed into the snow affecting its structure and the crystal's ability to maintain its form.