The word "trace" is used in many ways - something can "vanish without a trace" or you can "trace the outline of a picture." But to a meteorologist, "trace" has yet another meaning.

When precipitation occurs, but is too little to measure, we say a "trace" has fallen. What's too little to measure? Well, for rain, the threshold is 1/100 of an inch. Anything less than that - a few sprinkles, or a light shower - we call it a trace, and write a capital T on the official observation sheet.

For solid precipitation - snow and sleet - anything less than 1/10 of an inch is considered a trace.

To give you an idea how often a trace is observed, we average about 45 days per year with a trace of precipitation, with about 10 of those days being from snow.