The Largest Snowflake Ever Recorded Was 38 Centimeters Wide

On January 28, 1887, an extraordinary weather event occurred at Fort Keogh, a military post in the Montana Territory. Soldiers at the fort witnessed the fall of what is still recognized by the Guinness World Records as the largest snowflake ever observed. A rancher in the area, Matt Coleman, is credited with measuring one of these colossal flakes, reporting its diameter to be an astounding 15 inches (38 centimeters) and its thickness at 8 inches. He was quoted in the *Monthly Weather Review* as saying the flakes were "larger than milk pans." While no photographic evidence exists from that day, the record has stood for over a century. The winter of 1886-1887 was noted for its severity in the region, which may have contributed to the unusual meteorological event.

The formation of such a massive snowflake is a fascinating, though not entirely uncommon, meteorological phenomenon. It was not a single, giant ice crystal, but rather what is known as an aggregate snowflake. These large flakes form when weather conditions are just right, typically with temperatures hovering near the freezing point and very light winds. These conditions allow individual snow crystals, which are often wet and sticky, to collide (Review) and clump together as they fall. The more crystals that join the cluster, the larger the resulting aggregate snowflake becomes.

While most individual snow crystals are small, the process of aggregation can lead to impressively large snowflakes. The 1887 event in Montana, however, remains an extreme and captivating example of this natural process. The unique combination of ample moisture and calm atmospheric conditions allowed for the formation of a snowflake of a size that has not been officially documented since. This remarkable occurrence serves as a testament to the varied and sometimes surprising forms that weather can take.