January 31: ORD

Today is January 31st. It's the 31st day of the year. 335 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 32 and the normal low is 17. I've calculated the 33-year averages at 32 and 16.

On the warm side, in 1989 the high was the record high of 65 (O'Hare's only 60s high of the date) with a low of 40 (O'Hare's warmest low). In the prior year of 1988, the high was 55 (O'Hare's only 50s high of the date) with a low of 36. Five years later, in 1993, the high was 46 with a low of 31. Six years after that, in 1999, the high was 40 (our most recent 40s high) with a low of 32. In the prior year of 1998, the high was 41 with a low of 28. The other warm highs were 45 in 1990 and 44 in 1997. The other warm lows were 32 in 2003, 30 in 2002 and 30 in 2006. The record warmest low of 45 occurred way back in 1877, at a time when the official readings were taken adjacent to Lake Michigan. 22 of the past 33 highs (67%) were in the: 20s (10) and 30s (12). There were consecutive 20s & 30s highs as: six years from 1979 through 1984 and seven years from 2005 through 2011. On the warm side, seven highs (21%) were in the: 40s (5), 50s (1) and 60s (1). Three of the 40s highs came in the back to back to back years of 1997, 1998 and 1999 (44, 41 and 40). On the cold side, four highs (12%) were in the: single digits (1) and 10s (a.k.a. teens) (3). O'Hare's coldest high of the date is 1 degree in 1971.

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 16 with a low of 2, a cold day. In 1977 the high was 18 with a low of 4, a cold day. In 1974 the high was a warm 47 degrees. In 1972 the low was a cold zero degrees. In 1971 the high was 1 with a low of -4, a five degree spread, year of the record coldest high of 1 (at Midway) and a cold day. In 1970 the high was 46 with a low of 29, a warm day. In 1968 the high was 49 with a low of 35, a warm day. In 1967 the high was 35 with a low of 28, a seven degree spread. In 1966 the high was 16 with a low of -1, a cold day. In 1965 the high was 15 with a low of -6, a cold day. In 1964 the low was a warm 29 degrees. In 1963 the high was 14 with a low of -12, a cold day. In 1962 the high was 17 with a low of -2, a cold day. In 1959 the high was 9 with a low of -3, a cold day.

More recently, there were small spreads of three degrees in 2003 (35/32), four degrees in 2002 (34/30) and six degrees last year in 2011 (26/20). There was a large spread of 31 degrees three years ago in 2009 (38/7).

On the cold side, in 1996 the high was 6 with a low of -11. A decade and a year earlier, in 1985, the high was 16 with the record low of -12. That record low of -12 originally occurred way back in 1899. In 2004 the high was 14 with a low of -6. A decade before, in 1994, the high was 13 with a low of -5. Five years ago, in 2007, the high was 20 with a low of 3. The other cold lows were 2 in 1984 and 3 in 1980. The record coldest high of 1 occurred in 1971 at Midway. 24 of the last 33 lows (73%) were in the: 10s (a.k.a. teens) (11), 20s (7) and 30s (6). There were seven consecutive lows in the 10s, 20s and 30s from 1997 through 2003. One of these was in the 10s and three each were in the 20s & 30s. Eight lows (24%) were in the: negative 10s (a.k.a. negative teens) (2), negative single digits (2) and single digits (4). O'Hare's coldest lows of the date are -12 in both 1963 and 1985. One low (3%) was in the warm 40s.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1993 the high was 46 with a low of 31, overall 15.5 degrees ABOVE normal. Then in 1994 the high was 13 with a low of -5, overall 19 degrees BELOW normal.

Today is a major day in O'Hare's snow history. In 2002, 7.2 inches fell. This was the second day of a two day, 12 inch storm which was 77% of the month's total of 15.5 inches. 2008 was the first day of a two day tally of 7.4 inches. 3.9 inches fell. Last year, 2011, was the start of a blizzard. It was the first of three days of the third biggest snowstorm in Chicago's history. A total of 21.2 inches fell at O'Hare and Rockford had 15.1 inches. O'Hare had just an inch today and Rockford had 0.8 inches with a lot more to come. This storm is famous for stranding many motorists on Lake Shore Drive in Chicago as its high winds created tall drifts.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:38 and sunrise is at 7:08. Sunset is at 17:06 and twilight ends at 17:36. There's a total of 9 hours, 58 minutes of daylight today and 10 hours, 58 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:37 and sunrise is at 7:07. The moon is waxing gibbous, having reached first quarter last night at 22:10. Illumination was 51% at midnight, will be 56% at noon and 60% at midnight tonight. Moonset was at 0:56 this morning. Moonrise is at 10:55 later this morning. Moonset is at 1:54 tomorrow morning. Moonlight time is 14 hours, 1 minute which is 23 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 tomorrow. Groundhog Day is in two days.