December 8: ORD

Today is December 8th. It's the 342nd day of the year. 23 days remain. It's week 49 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. Before this, the official site was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 37 and the normal low is 23. I've calculated the 33-year averages at 37 and 22.

On the warm side, in 1987 the high was 58 with a low of 38. In 1991 the high was 60 with a low of 36. The other warm high was 49 in 1999. The other warm lows were 36 in 1986, 36 in 2004 and 35 in 2003. The record high of 64 and record warmest low of 53 were set on the same warm day in 1946 at Midway. 31 of the past 33 highs (94%) were in the: 20s (8), 30s (12) and 40s (11). Our most recent 40s highs were 45 in 2003 and 41 in 2004. Two highs were in the warm: 50s (1) and 60s (1). O'Hare's warmest temperature for the date was 61 in 1966. There were two sub-20 degree highs prior to 1978: 13 in 1958 and 14 in 1976.

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 cold 24 with a low of 13, a cold day. In 1976 the high was 14 with a low of 4, a cold day. In 1975 the high was 33 with a low of 28, a five degree spread. In 1973 the high was 34 with a low of 28, a six degree spread. In 1972 the high was 28 with a low of 21, a seven degree spread. In 1971 the high was 44 with a warm low of 40, a four degree spread and warm day. In 1970 the high was a warm 49 degrees. In 1967 the high was 40 with a warm low of 38, a two degree spread. In 1966 the high was 61 with a low of 37, a warm day. In 1964 the low was a cold 10 degrees. In 1958 the high was 13 with a low of -7, a cold day. That low of -7 equals the record low set way back in 1882.

More recently, there were no large spreads of 30 degrees or more. There were small spreads of three degrees in 1996 (30/27), four degrees in 1992 (28/24), five degrees in 1986 (41/36), five degrees in 1997 (31/26), five degrees in 2004 (41/36) and six degrees in 1983 (26/20).

On the cold side, in 2006 the high was 21 with a low of 4. A year earlier, in 2005, the high was 28 with a low of 3. Last year, in 2010, the high was 25 with a low of 7. In 1978 the high was 21 with a low of 11. In 1995 the high was 30 with a low of 4. Five years later, in 2000, the high was 29 with a low of 7. In 2007 the high was 24 with a low of 13. As you can see, 4 of the last 6 years were among the very coldest of the past 33 years. As for the two other years, 2008 (38/16) was slightly cold and 2009 (35/25) was normal. The record low of -7 was set way back in 1882. The record coldest high of 8 occurred back in 1927. Both records occurred at a time when the official readings were taken adjacent to Lake Michigan. 28 of the last 33 lows (85%) were in the: 10s (a.k.a. teens) (7), 20s (13) and 30s (8). Five lows were in the cold 0s (a.k.a. single digits). Our most recent 30s lows were 35 in 2003 and 36 in 2004. Prior to 1978, there were very cold lows of -7 in 1958 and 4 in 1976. O'Hare's warmest low for the date was 40 degrees in 1971.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:38 and sunrise is at 7:09. Sunset is at 16:21 and twilight ends at 16:53. There's a total of 9 hours, 12 minutes of daylight today and 10 hours, 15 minutes between twilights. We lost a minute of daylight from yesterday. Tomorrow twilight begins at 6:38 and sunrise is at 7:10. The moon is waxing gibbous and will reach the full Cold or Long Nights moon in two days at 8:36. Illumination was 95% at midnight, will be 97% at noon and 98% at midnight tonight. Moonset is at 5:20 this morning. Moonrise is at 15:01 this afternoon. Moonset is at 6:17 tomorrow morning. Moonlight time is 14 hours, 19 minutes which is 20 minutes longer than yesterday.

Winter began December 1st and runs for 102 days through March 11th. High temperatures in this period are usually in the 20s and 30s. Highs in the 40s and 50s occur infrequently. Bill of Rights Day is in seven days.