December 16: ORD

Today is December 16th. It's the 350th day of the year. 15 days remain. It's week 50 of the year.

Unless noted, the following data is based upon observations collected by the National Weather Service, Chicago, at O'Hare International Airport (ORD) between November 1978 and last year. ORD has been the official site of record for Chicago since Thursday, January 17, 1980.

According to the National Climatic Data Center (NCDC), the normal high is 34 and the normal low is 20. I've calculated the 32-year averages at 34 and 21.

On the warm side, in 1984 the high was the record high of 60 with a low of 37. In 2006 the high was 55 with a low of 32. Five years earlier, in 2001, the high was 45 with a low of 39, a six degree spread. In 1997 the high was 45 with a low of 32. Other warm lows were 35 in 1986, 34 in 1994, 33 in 1990, 33 in 1993 and 32 in 1998. The record warmest low of 43 was set back in 1928. Over the last 32 years, 28 highs (88%) were in the: 20s (7), 30s (13) and 40s (8). The most recent 30s high was 33 in 2002. The most recent 40s highs were 43 in 2003 and 43 in 2004. Two highs were in the warmer: 50s (1) and 60s (1). Two highs were in the cold: 0s (aka single digits)(1) and 10s (aka teens)(1).

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable: in 1977 the high was a warm 54 with a low of 30, a warm day. In 1974 the high was 36 with a low of 30, a six degree spread. In 1972 the high was 9 with a low of -2, a cold day. In 1971 the high was 39 with a warm low of 33, a six degree spread. In 1970 the high was 39 with a warm low of 36, a mere three degree spread. In 1966 the high was 34 with a warm low of 32, a mere two degree spread. In 1965 the high was 30 with a low of 24, a six degree spread. In 1963 the high was 15 with a low of -6, a cold day. In 1959 the high was 51 with a low of 35, a warm day. In 1958 the high was 36 with a cold low of 0, a 36 degree spread.

More recently, there was a large spread of 32 degrees in 1979 (37/5). There were small spreads of three degrees in 1980 (33/30), three degrees in 1990 (36/33), three degrees in 2002 (33/30), five degrees in 1986 (40/35), five degrees in 1994 (39/34), six degrees in 1996 (32/26), six degrees in 2005 (24/18) and seven degrees in 1993 (40/33).

On the cold side, in 1989 the high was 9 with a low of -5. A year earlier, 1988, the high was 17 with a low of 4. Three years prior, 1985, the high was 23 with a low of 3. Two years before that, 1983, the high was 23 with a low of 3. Last year the high was 23 with a low of 5. Two years ago the high was 22 with a low of 6. In 1981 the high was 22 with a low of 9. Other cold lows were 5 in 1979 and 6 in 1991. The record low of -12 and record coldest high of 2 were set on the same day in 1951. 19 of the last 32 lows (59%) were: 20s (7) and 30s (12). 13 lows (41%) were in the cold: negative 0s (1), 0s (aka single digits)(8) and 10s (aka teens)(4).

Yesterday was the second coldest December 15th of the past 33 years which puts it in the top 6% of coldest for the date. December 13th and 14th were the third coldest of the past 33 years which puts them as the top 9% of coldest for each date.

In 1973, O'Hare had 4.5 inches of snow today. This was the fourth day of a string of days through the 20th which produced 17.6 inches, or 94% of the month's total of 18.8 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight began at 6:44 and sunrise was at 7:16. Sunset is at 16:22 and twilight ends at 16:54. There's a total of 9 hours, 6 minutes of daylight today and 10 hours, 10 minutes between twilights. We are losing a minute of daylight per day. Tomorrow twilight begins at 6:45 and sunrise is at 7:16. The moon is waxing gibbous. Illumination was 74% at midnight, will be 79% at noon and 83% at midnight tonight. Moonset was at 2:20 this morning. Moonrise is at 12:58 this afternoon. Moonset is at 3:33 tomorrow morning. Moonlight time is 13 hours, 22 minutes which is 24 minutes longer than yesterday.

Christmas Eve is in eight days and Christmas Day is in nine days. -Bernie-