Historical Odds Of A White Christmas In Cincinnati

Snow is common during December in Cincinnati, but the odds of getting snow on the ground Christmas morning is lower than you might think.

A “White Christmas” is a Christmas Day where the snow depth at 7am is 1″ or higher. This snowfall amount is rounded to the nearest inch in official weather records. For example, a 7am snow depth of 0.5″ would be recorded as 1″ officially, and a snow depth at 7am of 0.4″ would be recorded as a “trace” officially. With this rounding considered, a 7am snow depth of 0.5″ or more on Christmas Day would mean a “White Christmas.”

7am snow depth records for Cincinnati have been taken since 1916 with one year (1947) missing. Based on weather records, it is hard to say if December 25, 1947 was a White Christmas. The official high temperature that day was 31°, and the low temperature that day was 14°. 0.03″ of precipitation was recorded at the Cincinnati/Northern Kentucky International Airport that day, but the 7am snow depth and the snowfall total for that day are missing. It is highly likely that the precipitation that fell that day was snow or nearly all snow. A 10-to-1 snow-to-liquid ratio would mean 0.3″ of snow fell that day. The snow-to-liquid ratio that day, however, is unknown.

At the time, official records were taken at the International Airport. However, weather records taken at the National Weather Bureau office in downtown Cincinnati suggest 1947 may have had a White Christmas:

dec21-wsorecords

At 7:30pm on December 25th, 1947, 0.5″ of snow was reported on the ground in downtown Cincinnati. 0.8″ fell that day, but it is unclear whether the 0.5″ of snow on the ground at 7:30pm that day was also on the ground at 7am Christmas Day. Regardless of what happened at the Weather Bureau office, it is not part of the official weather record for Cincinnati.

If you throw out Christmas Day 1947, there have been 16 White Christmases in Cincinnati since 1916:

dec21-whitexmaslist

16 White Christmases in 96 years worth of records shows there is, historically, a 17% chance of a White Christmas in the Queen City:

dec21-whitexmasmathnew

If you say 1947 was a White Christmas, there is, historically, a 18% chance of a White Christmas in Cincinnati:

dec21-whitexmasmathcounting1947

The math gets even more complicated if you include Christmas Day of 1992, which is the only year since 1916 where there was no snow on the ground at 7am but 1″ or more fell on that day after 7am. You could make an argument that 1992 had a White Christmas; if you believe it counts, the historical odds go up to 19%.

These historical odds are long-term. In the last 10 years, there have been 2 White Christmases in Cincinnati:

dec21-recentsnowdepths

The long-term average and the last 10 years suggest that a White Christmas happens in Cincinnati about once every 5 years. Back to 1916, the highest 7am snow depth recorded in Cincinnati on Christmas Day was in 2004 (9″).

Historically, the odds of a White Christmas Eve are about the same, but the years with a White Christmas and White Christmas Eve don’t always match up. Here is the list of years with 1″ or more of snow on the ground on Christmas Eve in Cincinnati:

dec21-whitexmasevelist

Weather records for Cincinnati are messy, but history suggests there is a 15 to 20% chance of a White Christmas any given year in the Queen City. We will know more about the likelihood of a White Christmas this year in the hours and days to come.

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