January 2015 is colder than most, but not unusual

This winter there is more ice on the Connecticut River than I have ever noticed before.  There are at least two factors: the weather, and the shutting of the nuclear reactor at Vermont Yankee, which will cool the thermal plume from the reactor.    I went to the weatherunderground web site history, and was able to collect the following data for the coldest of the winter months.   I collected the average temp and number of degree days for the past decade, and for the decade ending in 76, for a historical control.               I list the four winter months, the years, the mean average temperature, and the number of degree days.    At the bottom I have given the average (m) for the decade.                                                         data.1

Then I compare the average mean temp with the number of degree days, and this is what I found:

Degree days compare to average mean temp

Degree days compare to average mean temp

Thus, degree days correlate very strongly with average mean temp, which has a greater meaning to most.  Moreover, upon reflection they really are equivalent.   For  the example,  for Jan 2015 m=19 is equivalent to 1415 degree days.  Since the degree days are based on 65 degrees, then (65-19)times 31 equals 1426, an excellent approximation.    Degree days do not provide more information than average mean temp.

Thus, the data show that the average Jan temp for the past decade is 25, and the average for the 70’s decade is 24.  Temperatures of 19 or below have occurred twice in this decade, and three times in the 70’s decade.

Subsequently, I did a more detailed analysis of the  January, and this is subsequently what I found: the average is 24.6 +/- 4.6 degrees F.  The temperature of 19 is just over one standard deviation from the norm.

Jan temps

Thus, this January is colder than most,  but not unusual.  Historically,   February has been slightly warmer than January, but still below freezing.   There are six more scheduled weeks of winter.

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