February 4: ORD

Today is February 4th. It's the 35th day of the year. 331 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 29 and 14.

On the warm side, in 1991 the high was 51 with a low of 36 (O'Hare's warmest low of the date). A couple of years later, in 1993, the high was 52 (O'Hare's warmest of the date) with a low of 24. In 2008 the high was 44 with a low of 32. The other 50s highs in O'Hare's history for the date were all 50 degrees: in 1962, 1973 and 2005. The recent warm lows were 32 in 1986 and 31 in: 1992, 1997 and 1998. The record high of 59 was set way back in 1890 and the record warmest low of 37 occurred way back in 1909. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. 17 of the past 33 highs (52%) were in the: 20s (7) and 30s (10). On the warm side, eight highs (24%) were in the: 40s (5) and 50s (3). On the cold side, eight highs (24%) were in the: single digits (3) and 10s (a.k.a. teens) (5).

In looking back through the years to the first February at O'Hare in 1959, the following instances were notable: in 1978 the high was 22 with a cold low of 3, a cold day. In 1975 the low was a warm 31 degrees. In 1973 the high was 50 with a low of 34, a warm day. In 1972 the high was 9 with a low of -2, a cold day. In 1971 the high was 48 with a low of 31, a warm day. In 1970 the high was 34 with a cold low of -1, a 35 degree spread. In 1969 the high was 42 with a low of 10, a 32 degree spread. In 1966 the high was 20 with a low of -3, a cold day. In 1965 the high was 15 with a low of -10, a cold day. In 1964 the high was a warm 47 degrees with a low of 17, a 30 degree spread. In 1962 the high was 50 with a low of 32, a warm day.

More recently, there were small spreads of two degrees in 1998 (33/31), five degrees in 1986 (37/32), six degrees in 1997 (37/31) and seven degrees in 2006 (32/25).

On the cold side, in 1996 the high was 2 with the record low of -14. In 2007 the high was 2 with a low of -6. Those highs of 2 degrees are the coldest highs for the date in O'Hare's history. In 1981 the high was 10 with a low of -4. In 1989 the high was 7 with a low of 1, a six degree spread. A decade earlier, in 1979, the high was 12 with a low of -2. In 1985 the high was 19 with a low of -7. Three years before, in 1982, the high was 18 with a low of -2. Three years ago, in 2009, the high was 17 with a low of 0. In 1983 the high was 20 with a low of 3. In 2004 the high was 26 with a low of 0. The other cold high was 20 in 1994. The other cold low was 5 last year, in 2011. The record coldest high of 0 occurred in 1918, at a time when the official readings were taken adjacent to Lake Michigan. 17 of the last 33 lows (52%) were in the: negative single digits (5), single digits (7) and 10s (a.k.a. teens) (5). Our most recent 10s low was 10 in 2003. On the warm side, 15 lows (45%) were in the: 20s (9) and 30s (6). Even colder, one low (3%) was in the negative 10s (a.k.a. negative teens). Until the record low of -14 in 1996, O'Hare's coldest was -10 in 1965. Through Winter 2010-11, this is the average sixth coldest day of the year.

There was an instance of back-to-back-to-back years in which temperatures were just about as opposite as they can be. In 2007 the high was 2 with a low of -6, overall 27 degrees BELOW normal. Then in 2008 the high was 44 with a low of 32, overall 13 degrees ABOVE normal. Then in 2009 the high was 17 with a low of 0, overall 16.5 degrees BELOW normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:34 and sunrise is at 7:04. Sunset is at 17:11 and twilight ends at 17:41. There's a total of 10 hours, 7 minutes of daylight today and 11 hours, 7 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:33 and sunrise is at 7:03. The moon is waxing gibbous. Illumination was 86% at midnight, will be 89% at noon and 92% at midnight tonight. Moonset was at 4:31 this morning. Moonrise was at 14:06 this afternoon. Moonset is at 5:15 tomorrow morning. Moonlight time is 14 hours, 25 minutes which is 9 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. Abraham Lincoln's Birthday is in eight days. Valentine's Day is in ten days. Susan B. Anthony Day is in 11 days.