December 22: ORD

Today is December 22nd. It's the 356th day of the year. Nine days remain. It's week 51 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 33 and the normal low is 19. I've calculated the 33-year averages at 33 and 19.

On the warm side, in 1979 the high was 50 with a low of 44 (O'Hare's warmest low of the date), a six degree spread. In 2006 the high was 54 (O'Hare's warmest of the date) with a low of 40. In 2007 the high was 50 (our most recent 50s high) with a low of 36. Four years prior, in 2003, the high was 47 (our most recent 40s high) with a low of 36. A couple of years before that, in 2001, the high was 49 with a low of 33. In 1994 the high was 52 with a low of 27. The other warm highs were 48 in 1982 and 45 in 1988. The other warm lows were 33 in 1997 and 31 in 1981. The record high of 57 was set way back in 1875 (adjacent to Lake Michigan) and tied in 1957 at Midway. The record warmest low of 50 occurred back in 1941, at a time when the official readings were taken adjacent to Lake Michigan. 20 of the past 33 highs (61%) were in the: 30s (13) and 40s (7). Four highs (12%) were in the warm 50s. Nine highs (27%) were in the cold: single digits (3), 10s (a.k.a. teens) (4) and 20s (2). O'Hare's only single digit high prior to 1989 was 4 degrees in 1960. The two 20s highs were each 29 degrees, occurring in 1990 and 1995. Prior to 1979, O'Hare had recorded no highs in the warm 50s or lows in the warm 40s.

In looking back through the years to the first December at O'Hare in 1958, the following instances were notable: in 1974 the high was 42 with a cold low of 3, a 39 degree spread. In 1973 the high was 25 with a cold low of 3, a cold day. In 1972 the high was 33 with a warm low of 31, a mere two degree spread. In 1970 the high was 36 with a warm low of 34, a mere two degree spread. In 1967 the high was a cold 21 degrees. In 1965 the high was a warm 46 with a low of 29, a warm day. In 1963 the high was 19 with a low of -13, a 32 degree spread and cold day. In 1961 the high was 35 with a warm low of 31, a four degree spread. In 1960 the high was 4 with a low of -11, a cold day. That high of 4 is just a degree warmer than the record coldest high of 3 which occurred in 1989.

More recently, there was a large spread of 32 degrees in 2005 (38/6). There were small spreads of two degrees in 1981 (33/31), four degrees in 1997 (37/33), five degrees in 2002 (30/25), five degrees two years ago, in 2009 (32/27) and seven degrees in 1991 (36/29).

On the cold side, in 1989 the high was the record coldest high of 3 with a low of -12. In 2000 the high was 7 with a low of -9. In 1983 the high was 19 with a low of -18 (O'Hare's coldest of the date), a 37 degree spread. Three years ago, in 2008, the high was 7 with a low of -4. A decade earlier, in 1998, the high was 14 with a low of 5. In 2004 the high was 14 with a low of 8. In 1999 the high was 17 with a low of 8. Other cold lows were 5 in 1990 and 6 in 2005. The record low of -21 was set way back in 1872, at a time when the official readings were taken adjacent to Lake Michigan. 27 of the last 33 lows (82%) were in the: single digits (5), 10s (a.k.a. teens) (6), 20s (10) and 30s (6). Four lows were in the cold: negative 10s (2) and negative single digits (2). Prior to 1983, O'Hare had very cold lows of -13 in 1963 and -11 in 1960. Two lows were in the warm 40s.

There were three instances of back-to-back years in which temperatures were just about as opposite as they can be. 1. In 2000 the high was 7 with a low of -9, overall 27 degrees BELOW normal. Then in 2001 the high was 49 with a low of 33, overall 15 degrees ABOVE normal. 2. In 2003 the high was 47 with a low of 36, overall 15.5 degrees ABOVE normal. Then in 2004 the high was 14 with a low of 8, overall 15 degrees BELOW normal. 3. In 2007 the high was 50 with a low of 36, overall 17 degrees ABOVE normal. Then in 2008 the high was 7 with a low of -4, overall 24.5 degrees BELOW normal.

In 1969, O'Hare had 1.2 inches of snow today. This was the second of four days of a total of 13.5 inches of snow.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:47 and sunrise is at 7:19. Sunset is at 16:25 and twilight ends at 16:57. There's a total of 9 hours, 6 minutes of daylight today and 10 hours, 10 minutes between twilights. We gained a minute of daylight from yesterday. Tomorrow twilight begins at 6:48 and sunrise is at 7:20. The moon is waning crescent and will reach new in two days at 12:06. Illumination was 8% at midnight, will be 5% at noon and 3% at midnight tonight. Moonrise is at 5:02 this morning. Moonset is at 14:34 this afternoon. Moonrise is at 6:09 tomorrow morning. Moonlight time is 9 hours, 32 minutes which is 22 minutes shorter 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. Christmas Eve is in two days. Christmas is in three days.