Steamboat Springs and much of Colorado experienced an ‘unexpected’ snowfall on May 18-19, 2017.  But how ‘rare’ is several inches of snow in the middle of May?  The National Center Data on Climate (NCDC) is a repository for climate data.  A long-term (greater than 100 years), land-based record of climate (temperature, precipitation, snowfall) is available for Steamboat Springs.  Using this data, we can query the May snow events and get a feel for the likelihood of significant May snowfall.  Has it changed over the past 100 years? How might this impact gardening efforts in the Steamboat Springs area?

The figure below illustrates the daily snowfall in May.  The colors are parsed into weekly increments.  Blue and green indicate the first 2 weeks of the month whereas yellow and orange highlight snowfall that occurred in the last 2 weeks of the month.  Most ‘significant’ (greater than 5 inches – arbitrary distinction) occur in the first part of May (blue or green dots).  In 1944, 7 inches of snow fell on May 18.

 

Daily May Snowfall (inches) in Steamboat Springs parsed into weekly increments.

 

The graph below shows the sum of snow in May for each year.  Notice in 1944, Steamboat Springs received ~20 inches of snow that month (and 7 inches on May 18 – see graph above).  2017 was not the snowiest May, but at 11.5″ was significantly higher than the ~2.8″ average.  Most years with May snowfall greater than 10″, the snow comes in the first 2 weeks of the month.  It is relatively uncommon to get ‘significant’ snow fall after the middle of May.

 

May Monthly Snowfall (sum of all snow in May of each year)

 

The minimum temperature  (º F) of May over the past century shows a slight (possibly non-significant) upward increase from ~ 30º F to 33º F.  This warrants further investigation as it would impact the timing of safe gardening efforts.  If the nighttime minimum temperatures do not dip below freezing, it may be safe to plant that garden.  Keep in mind that there re sill plenty of early-May nights that dip below freezing (blue an green dots).

 

Minimum May Temperature (º F)

 

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