When do the first snowflakes usually fly?

With the possibility of a few slushy snowflakes mixing with rain drops next week let's look at when, on average, the first snowflakes are expected to fall in Northern Illinois.

Looking back over 30 years worth of data the average date that Rockford receives a trace of snow (less than 0.1") is usually around the 2nd of November.  The earliest snow has fallen was on back on the 3rd of October in 1951 with the latest December 19th, 1999.

Measurable snowfall (0.1" or more) on average occurs around the 20th of November with Northern Illinois receiving it's first inch of snow around the 1st of December.  Temperatures within the clouds on Saturday will be below freezing but remain above freezing at ground level.  This means that all we'll likely see are showers, rather than snowflakes.  There may, however, be a little graupel with any instability showers that develop.

 

By next week temperatures will be cold enough above and at the surface, especially at night, to support a mixture of rain and snow.  The highest time frame to experience this would be Tuesday night into Wednesday morning with the overnight low falling into the low 30s.