March 7: ORD

Today is March 7th. It's the 67th day of the year. 299 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 40 and 25.

On the warm side, in 2000 the high was the record high of 78 with the record warmest low of 53. In 1987 the high was the former record high of 74 with a low of 45. Four years earlier, in 1983, the high was 60 with a low of 44. In 1992 the high was 51 with a low of 44, a seven degree spread. The other warm highs were 57 in both 1988 and 2005. The other warm low was 39 three years ago in 2009. 19 of the past 33 highs (58%) were in the: 30s (10) and 40s (9). On the warm side, six highs (18%) were in the: 50s (3), 60s (1) and 70s (2). Prior to 1979, O'Hare had a warm high of 62 in 1973. On the cold side, eight highs (24%) were in the: 10s (a.k.a. teens) (2) and 20s (6).

In looking back through the years to the first March at O'Hare in 1959, the following instances were notable: In 1978 the high was a cold 30 with a low of 25, a five degree spread. In 1975 the high was 38 with a low of 31, a seven degree spread. In 1974 the low was a warm 40 degrees. In 1973 the high was 62 with a low of 44, a warm day. In 1971 the high was a cold 30 degrees. In 1968 the high was 54 with a low of 19, a 35 degree spread. In 1967 the high was a cold 30 with a low of 15, a cold day. In 1965 the high was 34 with a low of 30, a four degree spread. In 1960 the high was 24 with a low of 3, a cold day.

More recently, we had small spreads of four degrees in 1979 (37/33), five degrees in 2002 (38/33), six degrees three years ago in 2009 (45/39) and seven degrees in 2007 (28/21). The large spreads were 30 degrees in 1997 (49/19) and 30 degrees in 2005 (57/27).

On the cold side, in 1996 (O'Hare's coldest day of the date) the high was 17 (O'Hare's coldest high of the date) with a low of 5. A decade earlier, in 1986, the high was 18 with a low of 7. Four years before that, in 1982, the high was 20 with a low of 6. Two years later, in 1984, the high was 25 with a low of 11. In 2008 the high was 26 with a low of 14. In 1999 the high was 26 with a low of 15. A decade before that, in 1989, the high was 28 with a low of 17. The other cold high was 28 in 2007. The record low of -2 and record coldest high of 14 were set on the same cold day in 1943 at Midway. 14 of the last 33 lows (43%) were in the 20s. Nine lows (27%) were in the cold: single digits (3) and 10s (a.k.a. teens) (6). Ten lows (30%) were in the warm: 30s (6), 40s (3) and 50s (1). O'Hare's pre-1979 warm lows were 44 in 1973 and 40 in 1974. O'Hare's coldest reading of the date was 3 in 1960.

There were three instances of back-to-back years in which temperatures were just about as opposite as they can be. The first instance was a case of back-to-back-to-back years: in 1982 the high was 20 with a low of 6, overall 22 degrees BELOW normal. Then in 1983 the high was 60 with a low of 44, overall 17 degrees ABOVE normal. Then in 1984 the high was 25 with a low of 11, overall 17 degrees BELOW normal. In the second instance, in 1986 the high was 18 with a low of 7, overall 22.5 degrees BELOW normal. Then in 1987 the high was 74 with a low of 45, overall 24.5 degrees ABOVE normal. In the third instance, in 1999 the high was 26 with a low of 15, overall 14.5 degrees BELOW normal. Then in 2000 the high was 78 with a low of 53, overall 30.5 degrees ABOVE normal.

Today is a major day in Chicago's snow history. In 1999, 2.8 inches fell. This was the third of six days in which a total of 18.2 inches fell. Back in 1931 at the University of Chicago, where official stats for Chicago used to be kept, 10.9 inches fell.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:50 and sunrise is at 6:18. Sunset is at 17:51 and twilight ends at 18:19. There's a total of 11 hours, 33 minutes of daylight today and 12 hours, 29 minutes between twilights. We gained three minutes of daylight from yesterday. Tomorrow twilight begins at 5:48 and sunrise is at 6:16. The moon is waxing gibbous and will be full as the full Worm (a.k.a. Sap) moon tomorrow at 3:39. Illumination was 98% at midnight, will be 99% at noon and 100% at midnight tonight. Moonset is at 5:28 this morning. Moonrise is at 17:27 this afternoon. Moonset is at 5:59 tomorrow morning. Moonlight time is 12 hours, 1 minute which is 40 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 ten days.