March 6: ORD

Today is March 6th. It's the 66th day of the year. 300 days remain. It's week 10 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. ORD has been the official site of record for Chicago since Thursday, January 17, 1980. Before this, the official site of record 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 43 and the normal low is 26. I've calculated the 33-year averages at 42 and 25.

On the warm side, in 1983 (O'Hare's warmest March 6th) the high was the co-record high of 70 with the record warmest low of 53. In 1992 the high was 62 with a low of 47. Three years ago, in 2009, the high was 65 with a low of 39. In 2000 the high was the other co-record high of 70 with a low of 32, a 38 degree spread. Five years later, in 2005, the high was 64 with a low of 35. In 1994 the high was 58 with a low of 39. In 1987 the high was 67 with a low of 29, a 38 degree spread. 15 of the past 33 highs (46%) were in the 30s. On the warm side, 13 highs (39%) were in the: 40s (4), 50s (3), 60s (4) and 70s (2). O'Hare's warm days prior to 1979 were: 1973 (64/39) and 1974 (59/42). O'Hare also had a warm high of 55 in 1964. On the cold side, five highs (15%) were in the 20s.

In looking back through the years to the first March at O'Hare in 1959, the following instances were notable: In 1974 the high was 59 with a low of 42, a warm day. In 1973 the high was 64 with a low of 39, a warm day. In 1972 the high was 49 with a cold low of 12, a 37 degree spread. In 1969 the high was 39 with a low of 32, a seven degree spread. In 1966 the high was a cold 27 with a low of 21, a six degree spread. In 1965 the high was 33 with a low of 31, a two degree spread. In 1964 the high was a warm 55 with a low of 22, a 33 degree spread. In 1960 the high was 20 with a low of -1, year of the record low of 2 (at Midway) and a cold day.

More recently, we had small spreads of four degrees in 1995 (35/31) and six degrees in 1990 (32/26). The other large spread was 30 degrees in 1988 (51/21).

On the cold side, in 1982 the high was 24 with a low of 4. Two years earlier, in 1980, the high was 28 with a low of 6. In 2003 the high was 28 with a low of 11. Four years later, in 2007, the high was 24 with a low of 16. In 1996 the high was 30 with a low of 11. In 1984 the high was 27 with a low of 14. The other cold highs were 30 in 1989, 30 in 1999 and 31 in 1997. The record low of 2 was set in 1960 at Midway. The record coldest high of 15 was set back in 1932 at a time when the official readings were taken adjacent to Lake Michigan. 17 of the last 33 lows (52%) were in the 20s. Eight lows (24%) were in the cold: single digits (2) and 10s (a.k.a. teens) (6). O'Hare's coldest day of the date was in 1960 when the high was 20 and low was -1. Eight lows (24%) were in the warm: 30s (6), 40s (1) and 50s (1).

There was an instance of back-to-back-to-back years in which temperatures were just about as opposite as they can be. In 1982 the high was 24 with a low of 4, overall 20 degrees BELOW normal. Then in 1983 the high was 70 with a low of 53, overall 27.5 degrees ABOVE normal. Then in 1984 the high was 27 with a low of 14, overall 13.5 degrees BELOW normal.

Today is a major day in Chicago's snow history. In 1999, 1.6 inches fell. This was the second of six days in which a total of 18.2 inches fell.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:52 and sunrise is at 6:20. Sunset is at 17:50 and twilight ends at 18:18. There's a total of 11 hours, 30 minutes of daylight today and 12 hours, 26 minutes between twilights. We gained two minutes of daylight from yesterday. Tomorrow twilight begins at 5:50 and sunrise is at 6:18. The moon is waxing gibbous and will be full as the full Worm (a.k.a. Sap) moon in two days at 3:39. Illumination was 94% at midnight, will be 96% at noon and 98% at midnight tonight. Moonset is at 4:56 this morning. Moonrise is at 16:15 this afternoon. Moonset is at 5:28 tomorrow morning. Moonlight time is 12 hours, 41 minutes which is 38 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. St. Patrick's Day is in 11 days.