November 7: ORD

Today is November 7th. It's the 312th day of the year. 54 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 36. I've calculated the 34-year averages at 52 and 35.

On the warm side, three years ago, in 2009, the high was 71 (with 1966, O'Hare's warmest high of the date) with a low of 46. In 2001 the high was 68 (O'Hare's second warmest high of the date) with a low of 44. The other warm high was 67 degrees in 1982 (with 1975, O'Hare's third warmest high of the date). The other warm lows were 51 degrees last year in 2011 and 49 degrees in 1965. The record high of 75 degrees was set in 1915, at a time when the official readings were taken adjacent to Lake Michigan. The record warmest low of 63 degrees occurred in 1975 at Midway. 25 of the past 34 highs (74%) were in the: 40s (11) and 50s (14). There were eight consecutive 40s and 50s highs from 1993 through 2000. Seven highs (20%) were in the warm: 60s (6) and 70s (1). Two highs (6%) were in the cold: 20s (1) and 30s (1). O'Hare's warmest November 7th was in 1975 as the high was 67 (with 1982, O'Hare's third warmest high of the date) with a low of 62 (O'Hare's warmest low of the date). O'Hare's second warmest November 7th was in 1966 as the high was 71 (with 2009, O'Hare's warmest high of the date) with a low of 50. The other warm 11/7 was in 1977 (high of 58, low of 54 (O'Hare's second warmest low of the date)). 

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 58 with a warm low of 54, a spread of four degrees and a warm day. In 1976 the high was 38 with a low of 22, a cold day. In 1975 the high was 67 with a low of 62, a spread of just five degrees, a warm day and year of the record warmest low of 63. In 1971 the high was 35 with a low of 19, a cold day. In 1967 the low was a cold 22 degrees. In 1966 the high was 71 with a low of 50, a warm day. In 1965 the low was a warm 49 degrees. In 1959 the high was 35 with a low of 20, a cold day. In 1958 the low was a cold 24 degrees.

More recently, there were large spreads of 31 degrees in 1982 (67/36) and 30 degrees in 1981 (60/30). There were small spreads of four degrees in 1998 (42/38) and seven degrees last year, in 2011 (58/51).

On the cool side, in 1991 (O'Hare's coolest November 7th) the high was the record coolest high of 27 with the record low of 13. A couple of years later, in 1993, the high was 41 with a low of 16 (O'Hare's second coldest low of the date). The other cold lows were 22 degrees in 1967 and 24 degrees in 1958. The other cool high was 38 degrees in 1992. 19 of the last 34 lows (56%) were in the 30s. Six consecutive lows were in the 30s, from 1994 through 1999. Six lows (18%) were in the cold: 10s (2) and 20s (4). Our most recent 20s lows were 29 degrees in 2002 and 26 degrees in 2003. Nine lows (26%) were in the warm: 40s (8) and 50s (1). O'Hare's second coolest November 7th was in 1971 (high of 35, low of 19). O'Hare's third coolest 11/7 was in 1959 (high of 35, low of 20). The other cool day was in 1976 (high of 38, low of 22). O'Hare's second coolest highs of 35 degrees occurred in 1959 and 1971.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:05 and sunrise is at 6:34. Sunset is at 16:39 and twilight ends at 17:09. There's a total of 10 hours, 5 minutes of daylight today and 11 hours, 4 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:06 and sunrise is at 6:36. The moon reached last quarter  last night at 18:36. Illumination was 48% at midnight, will be 43% at noon and 38% at midnight tonight. Moonset is at 12:55 this afternoon. Moonrise is at 0:25 tomorrow morning. Moonset is at 13:24 tomorrow afternoon. Moonlight time is 12 hours, 55 minutes which is eight 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 20s, 60s and 70s occur infrequently. Veteran's Day is in four days.