February 13: ORD

Today is February 13th. It's the 44th day of the year. 322 days remain. It's week 7 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 35 and the normal low is 19. I've calculated the 33-year averages at 33 and 18.

On the warm side, in 1984 the high was 54 with the record warmest low of 40. 1984 is O'Hare's warmest February 13th. In 1990 the high was 54 with a low of 28. Last year, in 2011, the high was 45 with a low of 32. The other warm lows were 35 in 2005 and 31 in both 1998 and 2001. The record high of 63 was set back in 1938, at a time when the official readings were taken adjacent to Lake Michigan. 25 of the past 33 highs (76%) were in the: 20s (9) and 30s (16). O'Hare had two consecutive streaks of 20s & 30s highs as follows: seven years from 1991 through 1997 and six years from 1999 through 2004. On the warm side, seven highs (21%) were in the: 40s (5) and 50s (2). On the cold side, one high (3%) was in the 10s (a.k.a. teens). O'Hare's coldest high was 18 in 1975. The other pre-1979 cold high was 19 in 1970.

In looking back through the years to the first February at O'Hare in 1959, the following instances were notable: In 1976 the high was a warm 47 degrees. In 1975 the high was 18 with a low of 4, a cold day. In 1972 the high was 35 with a low of 29, a six degree spread. In 1971 the high was a cold 23 with a low of 8, a cold day. In 1970 the high was a cold 19 with a low of 7, a cold day. In 1963 the high was 23 with a cold low of -2, a cold day. In 1961 the high was 47 with a low of 33, a warm day. In 1959 the high was 37 with a warm low of 33, a four degree spread.

More recently, there were small spreads of two degrees in 2000 (31/29), six degrees in 2005 (41/35) and seven degrees in three years: 1979 (24/17), 1992 (34/27) and 2001 (38/31).

On the cold side, in 1988 the high was 19 with a low of -5. Two years earlier, in 1986, the high was 21 with a low of -6 (O'Hare's coldest low of the date). In 2008 the high was 21 with a low of 7. In 1982 the high was 25 with a low of 3. The other cold low was 5 in 1981. The other cold highs were both 23 degrees, in 1985 and 1995. The record low of -18 and record coldest high of -4 were set on the same cold day back in 1905, at a time when the official readings were taken adjacent to Lake Michigan. 22 of the last 33 lows (67%) were in the: 10s (a.k.a. teens) (13) and 20s (9). O'Hare had nine consecutive 10s & 20s lows from 1989 through 1997. Even colder, six lows (18%) were in the: negative single digits (2) and single digits (4). On the warm side, five lows (15%) were in the: 30s (4) and 40s (1).

Today is a major day in Chicago's snow history. In 2007, 8.8 inches fell. This was the second day of a three day, 11.6 inch storm.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:24 and sunrise is at 6:53. Sunset is at 17:23 and twilight ends at 17:52. There's a total of 10 hours, 30 minutes of daylight today and 11 hours, 28 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 6:23 and sunrise is at 6:52. The moon is waning gibbous. Illumination was 67% at midnight, will be 61% at noon and 55% at midnight tonight. Moonset is at 9:43 this morning. Moonrise is at 0:39 tomorrow morning. Moonset is at 10:26 tomorrow morning. Moonlight time is 9 hours, 43 minutes which is six 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. Valentine's Day is tomorrow. Susan B. Anthony Day is in two days. President's Day is in seven days.