February 1: ORD

Today is February 1st. It's the 32nd day of the year. 334 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 33 and 18.

On the warm side, in 1987 the high was 47 with a low of 34. Three years later, in 1990, the high was 52 with a low of 29. The previous year of 1989 registered a high of 52 with a low of 28. These highs (O'Hare's only 50s highs since 1968) occurred in back-to-back years! A decade later, in 1999, the high was 44 with a low of 35. More recently, in 2006, the high was 48 with a low of 31. In 1998 the high was 45 with a low of 33. In 1986 the high was 46 with a low of 30. In 1995 the high was 42 with a low of 32. The other warm low was 32 in 2003. The record high of 56 was set in 1968 at Midway. The record warmest low of 41 occurred way back in 1877, at a time when the official readings were taken adjacent to Lake Michigan. 16 of the past 33 highs (49%) were in the 30s. On the warm side, eight highs (24%) were in the: 40s (6) and 50s (2). O'Hare's warmest high was 54 in 1968. On the cold side, nine highs (27%) were in the: single digits (1), 10s (a.k.a. teens) (2) and 20s (6). O'Hare's coldest high (until 1985) was 5 in 1971.

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 18 with a low of 4, a cold day. In 1976 the high was 36 with a cold low of -3, a 39 degree spread. In 1973 the high was 48 with a low of 42, a six degree spread and warm day. In 1971 the high was 5 with a low of -5, a cold day. In 1970 the high was 47 with a low of 36, a warm day. In 1968 the high was 54 with a low of 37, a warm day and year of the record high of 56 at Midway. In 1966 the high was 27 with a cold low of -2 degrees, a cold day. In 1965 the high was 15 with a low of -4, a cold day. In 1962 the high was a cold 20 degrees. In 1960 the high was 34 with a low of 28, a six degree spread. In 1959 the high was 14 with a low of -3, a cold day.

More recently, there were small spreads of two degrees in 2003 (34/32), three degrees last year, in 2011 (23/20), five degrees in 1983 (33/28) and six degrees in 2008 (30/24).

On the cold side, in 1985 the high was 4 with the record low of -14. In 1996 the high was 10 with a low of -8 (our most recent negative single digit low). A couple of years earlier, in 1994, the high was 11 with a low of -9. In 1980 the high was 21 with a low of -1. A couple of years later, in 1982, the high was 23 with a low of -1. Three years earlier, in 1979, the high was 20 with a low of 5. The other cold low was 4 in 2001. The record coldest high of 3 occurred 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 (11) and 30s (7). O'Hare had consecutive years of lows in the 10s, 20s and 30s as follows: eight years from 1986 through 1993 and ten years from 2002 through 2011. O'Hare's warmest low of the date was 42 in 1973. Seven lows (21%) were in the cold: negative 10s (a.k.a. negative teens) (1), negative single digits (4) and single digits (2).

There were two instances of back-to-back years in which temperatures were just about as opposite as they can be. In the first instance, in 1985 the high was 4 with a low of -14, overall 29 degrees BELOW normal. Then in 1986 the high was 46 with a low of 30, overall 14 degrees ABOVE normal. In the second instance, in 1994 the high was 11 with a low of -9, overall 23 degrees BELOW normal. Then in 1995 the high was 42 with a low of 32, overall 13 degrees ABOVE normal. Then in 1996, the high was 10 with a low of -8, overall 23 degrees BELOW normal.

Today is a major day in O'Hare's snow history. Two years ago, in 2009, it was the second day of a two-day tally of 7.4 inches. 3.5 inches fell. Last year, 2011, was the start of a blizzard. It was the second 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 13.6 inches today and Rockford had 10.9 inches. 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 6:37 and sunrise is at 7:07. Sunset is at 17:07 and twilight ends at 17:37. There's a total of 10 hours of daylight today and 11 hours between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:36 and sunrise is at 7:06. The moon is waxing gibbous, having reached first quarter two nights ago at 22:10. Illumination was 60% at midnight, will be 65% at noon and 69% at midnight tonight. Moonset was at 1:54 this morning. Moonrise is at 11:33 later this morning. Moonset is at 2:50 tomorrow morning. Moonlight time is 14 hours, 21 minute which is 20 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 today. Groundhog Day is tomorrow.