A water molecule contains two hydrogen atoms, each of which is bonded by a polar covalent bond to an oxygen atom, in a near tetrahedral arrangement with the two lone electron pairs of the oxygen atom. Therefore, the H-O-H bond angle is about 107°. This polarity causes the intermolecular attraction known as hydrogen-bonding, and allows water molecules, at low temperatures, to aggregate in regular arrangements to form solid crystal lattices. You do remember all this from your High School Chemistry, don’t you?
In clouds, it is possible for very small water drops of 10µm or less to cool well below the so-called “freezing point” of water (0°C = 32°F), if there is nothing to trigger the aggregation. Then, suddenly, a number of molecules might come close enough to aggregate and form a tiny solid ice crystal. Because of the shape of the water molecules, and their polarity, the lattice in the ice crystal is hexagonal.
In the environment of a cloud, further crystallization can take place, with negligible influence by external forces such as gravity, so the structure can develop as multiple conjoined crystals in each of the six directions of the hexagon. Thus we get a six-pointed snowflake.
The process sounds clinical, when described in these terms. What is interesting is that, from a scientific observer’s point of view (though not from God’s) the process is at once, both random and organized. It is organized, to the extent that the hexagon is the dominant influence, but random in that crystals can aggregate in any manner. This gives rise to the wide variety of snowflake designs, and the myth that “no two snowflakes are the same”. Although the myth is not quite true, the chance of an individual finding two identical snowflakes is very small indeed.
Water, in all of its phases, is at once familiar, yet enigmatic; ubiquitous yet unique. Because there is so much water around on the earth, in solid, liquid and gaseous forms, we forget that many of its properties are startlingly unusual, compared to pretty much every other compound one can think of. For example, solid water (ice) floats on liquid water. So what? Well, every other solid that I can think of is denser than its liquid phase, so, for example, solid vegetable oil collects at the bottom of a bottle of oil on a cold day, not at the top. Yet, what would happen to fish living in a pond, if the pond froze from the bottom up, instead of the top down?
I have long thought that water shows all the hallmarks of a material especially designed for purpose. God has made it so that it works perfectly for this world, and the people, with whom He chose to populate it. But why the extravagant beauty, symmetry and artistry of the snowflake? I don’t know—except that He views everything He made as precious and as good. Perhaps the artistic value of the snowflake is part of what God was explaining to Job, when He referred to “the treasures of the snow”. (Job 38:22)