November 13: ORD

Today is November 13th. It's the 318th day of the year. 48 days remain. It's week 46 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. 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 50 and the normal low is 34. I've calculated the 34-year averages at 51 and 33.

On the warm side, in 1989 (O'Hare's warmest November 13th) the high was the record high of 73 with a low of 45. Five years later, in 1994 (O'Hare's second warmest November 13th), the high was 65 with the record warmest low of 52. Last year (2011, O'Hare's third warmest November 13th) the high was 70 (O'Hare's third warmest high of the date) with a low of 47. In 1993 the high was 65 with a low of 45. In 1999 the high was 71 (O'Hare's second warmest high of the date) with a low of 37, a 34 degree spread. The other warm highs were 64 degrees in 1978, 63 degrees in 1960 and 63 degrees in 2001. 24 of the past 34 highs (71%) were in the: 40s (8), 50s (8) and 60s (8). There were 11 consecutive highs in the 40s, 50s and 60s from 2000 through 2010. Three highs (9%) were in the warm 70s. Seven highs (20%) were in the cold: 20s (3) and 30s (4). No highs have been below 40 degrees from 1998 onward. The other warm November 13th days were in: 1958 (high of 65, low of 48) and 1973 (high of 61, low of 50 (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 1976 the high was 40 with a cold low of 17, a cold day. In 1975 the high was a cold 38 with a low of 32, a six degree spread. In 1974 the high was a cold 36 degrees. In 1973 the high was 61 with a warm low of 50, a warm day. In 1967 the high was a cold 38 degrees. In 1962 the high was 57 with a low of 26, a 31 degree spread. In 1960 the high was a warm 63 degrees. In 1959 the high was 35 with a low of 26, a cold day. In 1958 the high was 65 with a low of 48, a warm day.

More recently, there were no other large spreads. There was a small spread of three degrees in 1985 (46/43).

On the cool side, in 1986 (O'Hare's coolest November 13th) the high was the record coldest high of 21 with the record low of 6. A decade later, in 1996, the high was 27 (O'Hare's second coolest high of the date) with a low of 17 (tied with 1976 as O'Hare's second coldest low). In 1982 the high was 28 (O'Hare's third coolest high of the date) with a low of 20. In 1995 the high was 31 with a low of 18 (O'Hare's third coldest low of the date). Three years earlier, in 1992, the high was 36 with a low of 24. Five years later, in 1997, the high was 37 with a low of 24. In 1983 the high was also 37 with a low of 24. Note that the lows in the 10s (a.k.a. teens) happened in the back-to-back years of 1995 and 1996. 30 of the last 34 lows (88%) were in the: 20s (10) and 30s (12) and 40s (8). Our most recent 20s lows were 29 degrees in 2003 and 26 degrees in 2004. Three lows were in the cold: 0s (1) and 10s (2). One low was in the warm 50s. The other cool November 13ths were in: 1976 (high of 40, low of 17 (tied with 1996 as O'Hare's second coldest low of the date)) and 1959 (high of 35, low of 26). The other cool highs were 36 degrees in 1974, 38 degrees in 1967 and 38 degrees in 1975. 

There were two instances of back-to-back years in which temperatures were just about as opposite as they can be. In the first instance, in 1992 the high was 36 with a low of 24, overall 12 degrees BELOW normal. Then in 1993 the high was 65 with a low of 45, overall 13 degrees ABOVE normal. In the second instance, in 1994 the high was 65 with a low of 52, overall 16.5 degrees ABOVE normal. Then in 1995 the high was 31 with a low of 18, overall 17.5 degrees BELOW normal. Also interesting is that all of this occurred in four consecutive years!

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:12 and sunrise is at 6:42. Sunset is at 16:33 and twilight ends at 17:03. There's a total of 9 hours, 51 minutes of daylight today and 10 hours, 51 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:13 and sunrise is at 6:43. The moon reaches new today at 16:08. Illumination was 1% at midnight, will be 0% at noon and 0% at midnight tonight. Moonrise was at 6:21 this morning. Moonset is at 16:26 this afternoon. Moonrise is at 7:34 tomorrow morning. Moonlight time is 10 hours, 5 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 20s, 60s and 70s occur infrequently. Thanksgiving is in nine days.