Tuesday, November 6, 2012

November 6: ORD

Today is November 6th. It's the 311th day of the year. 55 days remain. It's week 45 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 was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. 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 53 and the normal low is 37. I've calculated the 34-year averages at 51 and 34.


On the warm side, in 2008 the high was 65 with a low of 45. In 1996 the high was 63 with a low of 45. In 2004 the high was 65 with a low of 42. O'Hare's warmest high (of the last 34 years) was 68 degrees in 1980 (also it's O'Hare's second warmest high of the date) but since the low was 28 degrees, the day was just three degrees above normal. However, the spread of 40 degrees is remarkable. The record high of 75 degrees was set in 1975 at Midway. The record warmest low of 63 degrees occurred in 1924, at a time when the official readings were taken adjacent to Lake Michigan.
23 of the past 34 highs (68%) were in the: 40s (11) and 50s (12). O'Hare recorded seven consecutive highs in the 40s and 50s from 1981 through 1987. Seven highs (20%) were in the warm 60s. Six of the 60s highs (86% of them) occurred in a 14 year span from 1996 through 2009. Included were 60s highs in the back-to-back years of 2004/2005 and 2008/2009. Four highs (12%) were in the cold 30s. All of the 30s highs occurred in a six year span from 1988 through 1993, including three consecutive from 1991 through 1993. O'Hare's warmest November 6th was in 1975 as the high was 75 (O'Hare's warmest high of the date and only 70s high) with a low of 57 (O'Hare's warmest low of the date). O'Hare's second warmest 11/6 was in 1965 as the high was 64 with a low of 55 (O'Hare's second warmest low of the date). O'Hare's third and most recent 50s low is 52 degrees in 1977.  

In looking back through the years to the first November at O'Hare in 1958, the following instances were notable: in 1977 the high was 59 with a warm low of 52, a spread of seven degrees. In 1975 the high was 75 with a low of 57, a warm day and year of the record high of 75, set at Midway. In 1973 the high was 41 with a low of 20, a cold day. In 1971 the low was a cold 24 degrees. In 1969 the high was 60 with a low of 30, a 30 degree spread. In 1968 the high was 48 with a low of 45, a three degree spread. In 1965 the high was 64 with a warm low of 55, a warm day. In 1961 the high was 40 with a low of 23, a cold day. In 1960 the high was a cold 41 degrees. In 1959 the high was 30 with a low of 24, a six degree spread, cold day and year of the record coldest high of 29 at Midway.


More recently, the only large spread (30 degrees or more) was 40 degrees in 1980 (68/28). There were additional small spreads of four degrees in 1997 (47/43), seven degrees in 1989 (49/42) and seven degrees in 2002 (43/36). 

On the cool side, in 1993 (O'Hare's coolest November 6th) the high was 32 (O'Hare's second coolest high of the date) with a low of 20 (with 1973, O'Hare's second coldest low of the date). A couple of years earlier, in 1991 (O'Hare's third coolest November 6th), the high was 36 with the record low of 19. Three years earlier, in 1988, the high was 36 with a low of 31, a five degree spread. Four years later, in 1992, the high was 37 with a low of 31, a six degree spread. The other cold lows were 23 degrees in 1984, 24 degrees in 1971, 25 degrees in 1982 and 25 degrees two years ago, in 2010. The other cool high of 41 degrees occurred in 1960. The record coolest high of 29 degrees occurred in 1959 at Midway. 18 of the last 33 lows (53%) were in the 30s. Seven lows (21%) were in the cold: 10s (1) and 20s (6). Five of the 20s lows (83% of them) occurred in a 14 year span from 1980 through 1993. Nine lows (26%) were in the warm 40s. Eight of the 40s lows (89% of them) occurred in a 16 year span from 1996 through 2011, including two in a row (1996/1997) and three in a row (2004-6). O'Hare's second coolest November 6th was in 1959 as the high was 30 (O'Hare's coolest high of the date) with a low of 24. The other cool 11/6 days were in: 1973 (high of 41, low of 20 (with 1993, O'Hare's second coldest low of the date)) and 1961 (high of 40, low of 23). 

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:04 and sunrise is at 6:33. Sunset is at 16:40 and twilight ends at 17:10. There's a total of 10 hours, 7 minutes of daylight today and 11 hours, 6 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:05 and sunrise is at 6:34. The moon reaches last quarter tonight at 18:36. Illumination was 58% at midnight, will be 53% at noon and 48% at midnight tonight. Moonset is at 12:24 this afternoon. Moonrise is at 23:21 tonight. Moonset is at 12:55 tomorrow afternoon. Moonlight time is 13 hours, 3 minutes which is 29 minutes shorter than yesterday.

Cool Fall began on November 2nd and runs for 29 days through November 30th. High temperatures in this period are usually in the 30s, 40s and 50s. Highs in the 10s and 20s occur infrequently. Election Day is today. Veteran's Day is in five days.

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