December 5: ORD

Today is December 5th. It's the 339th day of the year. 26 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 38 and the normal low is 24. I've calculated the 33-year averages at 39 and 24.

On the warm side, in 1998 the high was 62 with the record warmest low of 55, a seven degree spread. Three years later, in 2001, the high was the record high of 68 (our most recent 60s high) with a low of 44. In 1982 the high was 63 with a low of 38. Three years prior, in 1979, the high was 54 with a low of 37. A year later, in 1980, the high was 55 with a low of 36. The 50s highs, as you can see, occurred in back to back years quite some time ago (1979 & 1980). In 1994 the high was 49 with a low of 37. 27 of the past 33 highs (82%) were in the: 20s (7), 30s (11) and 40s (9). There were 15 consecutive 20s, 30s and 40s highs from 1983 through 1997. Our most recent 40s highs were 47 in 2004 and 43 in 2003. Five highs were in the warm: 50s (2) and 60s (3). The pre-1978 50s & 60s highs were 64 in 1975, 61 in 1960 and 51 in 1965. One high was in the cold 10s.

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable: in 1976 the low was a cold 9 degrees. In 1975 the high was 64 with a low of 46, a warm day. In 1972 the high was 30 with a low of 24, a six degree spread. In 1971 the high was 40 with a warm low of 36, a four degree spread. In 1967 the high was 48 with a warm low of 39, a warm day. In 1966 the high was 39 with a low of 34, a five degree spread. In 1965 the high was a warm 51 degrees. In 1964 the high was 23 with a low of 8, a cold day. In 1960 the high was 61 with a low of 41, a warm day. In 1958 the low was a cold 11 degrees.

More recently, there were no large spreads. There were small spreads of three degrees in 1996 (34/31), five degrees in 1978 (36/31), five degrees in 1983 (37/32) and six degrees in 1997 (29/23).

On the cold side, in 2005 the high was 17 with the record low of 4. Three years later (also three years ago) in 2008, the high was 23 with a low of 7. Two years after that (last year) in 2010, the high was 26 with a low of 12. Four years ago, in 2007, the high was 30 with a low of 9. In 2002 the high was 24 with a low of 15. A decade before that, in 1992, the high was 25 with a low of 14. The year prior, in 1991, the high was 33 with a low of 6, the first single-digit low since 1976. In 1984 the high was 28 with a low of 11. The other cold lows were 7 in 2006 and 12 in 2000. The record coldest high of 15 was set way back in 1895, at a time when the official readings were taken adjacent to Lake Michigan. 26 of the last 33 lows (79%) were in the: 10s (a.k.a. teens)(8), 20s (7) and 30s (11). Many of the 10s, 20s and 30s lows occurred in 14 consecutive years from 1977 through 1990 and six consecutive years from 1992 through 1997. Our most recent 30s low was 31 in 2003. Five lows were in the cold 0s (a.k.a. single digits). The pre-1978 single-digit lows were 8 in 1964 and 9 in 1976. Two lows were in the warm: 40s (1) and 50s (1). Four of the five single digit lows occurred four years in a row from 2005 to 2008, including the record low of 4 in 2005.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 2001 the high was 68 with a low of 44, overall 25 degrees ABOVE normal. Then in 2002 the high was 24 with a low of 15, overall 11.5 degrees BELOW normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:35 and sunrise is at 7:06. Sunset is at 16:21 and twilight ends at 16:53. There's a total of 9 hours, 15 minutes of daylight today and 10 hours, 18 minutes between twilights. We lost a minute of daylight from yesterday. Tomorrow twilight begins at 6:36 and sunrise is at 7:07. The moon is waxing gibbous, having reached first quarter three days ago at 3:52. Illumination was 76% at midnight, will be 80% at noon and 83% at midnight tonight. Moonset is at 2:24 this morning. Moonrise is at 13:22 this afternoon. Moonset is at 3:23 tomorrow morning. Moonlight time is 13 hours, 2 minutes which is 33 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. Pearl Harbor Day is in two days. Bill of Rights Day is in ten days.