November 9: ORD

Today is November 9th. It's the 314th day of the year. 52 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 52 and the normal low is 35. I've calculated the 34-year averages at 52 and 36.

On the warm side, in 1999 (O'Hare's warmest November 9th) the high was the record high of 74 with the record warmest low of 59. Three years later, in 2002, the high was 63 with a low of 53 (O'Hare's second warmest low of the date). Four years later, in 2006, the high was 68 with a low of 47. Three years later (three years ago), in 2009, the high was 63 with a low of 50. In 1984 the high was 62 with a low of 49. The other warm highs were 69 degrees two years ago in 2010, 66 degrees in 1977 and 66 degrees in 2005. The other warm low was 49 degrees in 1970. The day is divided into a warm and cool sector. On the warm side, 17 of the past 34 highs (50%) were in the: 50s (6), 60s (10) and 70s (1). Our most recent 50s high was 53 degrees in 2004. On the cool side, 17 highs (50%) were in the: 30s (3) and 40s (14). O'Hare's second warmest November 9th was in 1975 as the high was 68 with a low of 52. The other warm 11/9 days were: 1964 (high of 71 (O'Hare's second warmest high of the date), low of 45) and 1966 (high of 63, low of 48).  

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 a warm 66 degrees. In 1975 the high was 68 with a low of 52, a warm day. In 1973 the high was 34 with a low of 20, a cold day. In 1972 the high was 45 with a low of 41, a four degree spread. Also in 1972, the temperatures from the 9th to the 11th were the same (a high of 45 and low of 41 each day). On the 12th, the high was 46 with a low of 41. In 1971 the high was a cold 40 with a low of 34, a six degree spread. In 1970 the low was a warm 49 degrees. In 1969 the high was 48 with a low of 41, a seven degree spread. In 1968 the high was a cold 40 degrees. In 1966 the high was 63 with a warm low of 48, a warm day. In 1964 the high was a warm 71 with a low of 45, a warm day. In 1960 the low was a cold 23 degrees.

More recently, there were no additional large spreads of at least 30 degrees (see "cool side" below). There were small spreads of four degrees in 1982 (46/42), five degrees in 1997 (45/40), six degrees in 1990 (40/34) and six degrees in 2000 (42/36).
 
On the cool side, in 1991 (O'Hare's coolest November 9th) the high was 37 (O'Hare's second coolest high of the date) with the record low of 14. Five years prior, in 1986, the high was 39 with a low of 21. In 2003 the high was 41 with a low of 20. In 1995 the high was 48 with a low of 17 (O'Hare's second coldest low of the date), a 31 degree spread. The other cold low was 23 degrees in 1960. The other cool highs were 39 degrees in 2008 and 40 degrees in: 1968, 1971, 1990 and 1996. The record coolest high of 31 degrees was set in 1957 at Midway. 29 of the last 34 lows (85%) were in the: 20s (8), 30s (9) and 40s (12). Our most recent 20s low was 20 degrees in 2003. Two lows were in the cold 10s (a.k.a. teens), the only ones thus far in O'Hare's history for the date. Three lows were in the warm 50s. O'Hare's second coolest November 9th was in 1973 as the high was 34 (O'Hare's second coolest high of the date) with a low of 20.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 2002 the high was 63 with a low of 53, overall 14 degrees ABOVE normal. Then in 2003 the high was 41 with a low of 20, overall 13.5 degrees BELOW normal. 

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:07 and sunrise is at 6:37. Sunset is at 16:37 and twilight ends at 17:07. There's a total of 10 hours of daylight today and 11 hours between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:08 and sunrise is at 6:38. The moon is waning crescent. Illumination was 28% at midnight, will be 23% at noon and 18% at midnight tonight. Moonrise was at 1:31 this morning. Moonset is at 13:54 this afternoon. Moonrise is at 2:39 tomorrow morning.  Moonlight time is 12 hours, 23 minutes which is 36 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 two days. Thanksgiving is in 13 days.