January 29: ORD

Today is January 29th. It's the 29th day of the year. 337 days remain. It's week 5 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. Observations have been official at O'Hare 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 31 and the normal low is 17. I've calculated the 33-year averages at 32 and 16.

On the warm side, in 2006 the high was 50 with a low of 39, O'Hare's warmest low of the date. In 1989 the high was 42 with a low of 37, a five degree spread. In 1998 the high was 41 with a low of 32. A decade earlier, in 1988, the high was 50 with a low of 22. Five years before, in 1983, the high was 41 with a low of 30. In 2001 the high was 42 with a low of 29. The other warm highs were 48 in 2008 and 45 in 1990. The other warm low was 31 in 2002. 2008 was what I call a dual day. The high qualifies as one of the warmest (48 degrees) and the low is one of the coldest at 2 degrees, a huge 46 degree spread. A cold front moved in, causing a temperature crash. The record high of 59 was set back in 1914 and record warmest low of 38 occurred a decade later in 1924. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. 23 of the past 33 highs (70%) were in the: 20s (12) and 30s (11). O'Hare had seven consecutive 20s & 30s highs from 1991 through 1997. On the warm side, eight highs (24%) were in the: 40s (6) and 50s (2). O'Hare's warmest high of the date was 51 in 1968. On the cold side, two highs (6%) were in the: single digits (1) and 10s (a.k.a. teens) (1). O'Hare's coldest highs of the date are -6 in 1966 and -1 in 1965.

In looking back through the years to the first January at O'Hare in 1959, the following instances were notable: in 1978 the high was 13 with a low of -5, a cold day. In 1977 the high was 8 with a low of -2, a cold day. In 1972 the high was 14 with a low of -6, a cold day. In 1969 the high was 48 with a low of 34, a warm day. In 1968 the high was 51 with a low of 35, a warm day. In 1966 the high was -6 with a low of -20, an extremely cold day. 1966 was the year of both the record low of -16 and record coldest high of -6 at Midway. In 1965 the high was -1 with a low of -11, a cold day. In 1963 the high was 17 with a low of 1, a cold day. In 1961 the high was 16 with a low of -6, a cold day. In 1960 the high was 34 with a warm low of 30, a four degree spread. In 1959 the high was 36 with a warm low of 29, a seven degree spread.

More recently, there were small spreads of five degrees in 2002 (36/31), six degrees in 1992 (33/27) and seven degrees last year in 2011 (33/26). The large spreads were 33 degrees in 1982 (34/1) and that unusual day four years ago in 2008 when the high was 48 and then the crash to 2 degrees, a 46 degree spread.

On the cold side, in 2004 the high was 4 with a low of -1, a five degree spread. In 1997 the high was 20 with a low of -6. In 1980 the high was 16 with a low of 0. Five years later, in 1985, the high was 22 with a low of 0. The other cold lows were 1 in 1982, 2 in 2008, 5 in 1996 and 5 two years ago in 2010. The record low of -16 and the record coldest high of -6 were set on the same cold day in 1966 at Midway. The record low of -16 was originally set way back in 1873, at a time when the official readings were taken adjacent to Lake Michigan. 26 of the last 33 lows (79%) were in the: single digits (9), 10s (a.k.a. teens) (8) and 20s (9). Two lows (6%) were in the cold negative single digits. O'Hare's coldest lows of the date were -20 in 1966 and -11 in 1965. Five lows (15%) were in the warm 30s.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1997 the high was 20 with a low of -6, overall 17 degrees BELOW normal. Then in 1998 the high was 41 with a low of 32, overall 12.5 degrees ABOVE normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:40 and sunrise is at 7:10. Sunset is at 17:03 and twilight ends at 17:33. There's a total of 9 hours, 53 minutes of daylight today and 10 hours, 53 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:39 and sunrise is at 7:09. The moon is waxing crescent and will reach first quarter tomorrow at 22:10. Illumination was 32% at midnight, will be 37% at noon and 41% at midnight tonight. Moonrise is at 9:53 this morning. Moonset is at 23:58 tonight. Moonrise is at 10:22 tomorrow morning. Moonlight time is 14 hours, 5 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. National Freedom Day is in three days. Groundhog Day is in four days.