February 18: ORD

Today is February 18th. It's the 49th day of the year. 317 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 36 and the normal low is 21. I've calculated the 33-year averages at 38 and 22.

On the warm side, in 1981 the high was the record high of 62 with the record warmest low of 45. The record high of 62 was originally set in 1961 at Midway. In 1997 the high was 55 with a low of 42. Three years earlier, in 1994, the high was 57 with a low of 38. A year later, in 1995, the high was 55 with a low of 29. Last year, in 2011, the high was 50 with a low of 33. In 1984 the high was 47 with a low of 35. In 1992 the high was 46 with a low of 35. The other warm high was 50 in 2002. The other warm lows were 37 in 1998, 34 in 1991 and 33 in 1986. 19 of the past 33 highs (58%) were in the: 30s (10) and 40s (9). O'Hare recorded seven consecutive 30s & 40s highs from 1982 through 1988. Our most recent 40s high was 43 in 2004. On the warm side, six highs (18%) were in the: 50s (5) and 60s (1). Prior to 1979, O'Hare had highs of 60 in 1961 and 52 in 1976. On the cold side, eight highs (24%) were in the: single digits (1), 10s (a.k.a. teens) (2) and 20s (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 low of -2, a cold day. In 1976 the high was 52 with a low of 35, a warm day. In 1975 the high was 33 with a low of 31, a two degree spread. In 1974 the high was 49 with a low of 33, a warm day. In 1971 the high was 45 with a warm low of 38, a seven degree spread and warm day. In 1968 the low was a cold 7 degrees. In 1963 the high was a warm 48 degrees. In 1962 the high was 31 with a low of 26, a five degree spread. In 1961 the high was a warm 60 with a low of 29, a 31 degree spread and warm day. 1961 was the year that the record high of 62 was originally set at Midway. In 1959 the high was 21 with a low of 6, a cold day.

More recently, there were small spreads of three degrees in 1998 (40/37), four degrees in 1982 (35/31), four degrees in 2000 (32/28), six degrees in 1983 (38/32) and seven degrees in 1986 (40/33).

On the cold side, in 2006 the high was 8 with a low of -7. 2006 was O'Hare's coldest February 18th. In 1979 the high was 12 with a low of 0. In 1993 the high was 18 with a low of -3. In 2007 the high was 22 with a low of 11. The other cold lows were 7 degrees in 1980, 2001 and 2008. The record low of -14 and record coldest high of 0 were set on the same cold day back in 1936, at a time when the official readings were taken adjacent to Lake Michigan. 29 of the last 33 lows (88%) were in the: single digits (5), 10s (a.k.a. teens) (6), 20s (9) and 30s (9). On the cold side, two lows were in the negative single digits. O'Hare's only pre-1979 sub-zero low was -2 in 1978. On the warm side, two lows were in the 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 18 with a low of -3, overall 20.5 degrees BELOW normal. Then in 1994 the high was 57 with a low of 38, overall 19.5 degrees ABOVE normal.

Today is a major day in Chicago's snow history. Back in 1908 at the U.S. Courthouse, 11.5 inches fell. In 2000, 11.1 inches fell and this accounted for 96% of the month's total of 11.6 inches.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:17 and sunrise is at 6:46. Sunset is at 17:29 and twilight ends at 17:58. There's a total of 10 hours, 43 minutes of daylight today and 11 hours, 41 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 6:16 and sunrise is at 6:45. The moon is waning crescent. Illumination was 15% at midnight, will be 11% at noon and 8% at midnight tonight. Moonrise is at 4:28 this morning. Moonset was at 14:23 this afternoon. Moonrise is at 5:07 tomorrow morning. Moonlight time is 9 hours, 55 minutes 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. Presidents' Day is in two days. Mardi Gras is in three days. George Washington's Birthday and Ash Wednesday are in four days.