November 23: ORD

Today is November 23rd. It's the 327th day of the year. 38 days remain. It's week 47 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. 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 44 and the normal low is 29. I've calculated the 33-year averages at 46 and 29.

On the warm side, in 1999 the high was 63 with a low of 40. Two years later, in 2001, the high was 59 with a low of 44 (along with a low of 44 in 1968, O'Hare's warmest lows). In 1998 the high was 60 with a low of 40. The other warm highs were 65 in 2003 (our most recent 60s high and O'Hare's warmest high), 60 in 1983 and 58 in 2006. The other warm low was 41 two years ago, in 2009. The record high of 69 and record warmest low of 62 were set on the same warm day back in 1931, a time when the official readings were taken adjacent to Lake Michigan. 22 of the past 33 highs (67%) were in the: 30s (10) and 40s (12). Ten highs (30%) were in the warm: 50s (6) and 60s (4). There were two pre-1978 highs in the 60s: 62 in 1966 and 61 in 1974. One high (3%) was in the cold 20s. There was just one pre-1978 high in the 20s: 21 in 1970.

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 38 with a low of 33, a five degree spread. In 1976 the high was a cold 31 degrees. In 1974 the high was a warm 61 with a low of 40, a warm day. In 1972 the high was a cold 31 degrees. In 1971 the high was a cold 32 degrees. In 1970 the high was 21 with a low of 10, a cold day. In 1968 the high was 55 with a warm low of 44, a warm day. In 1966 the high was 62 with a low of 53, a warm day. In 1958 the high was a warm 58 degrees.

More recently, there were large spreads of 35 degrees in 2003 (65/30) and 31 degrees in 1983 (60/29). There were small spreads of two degrees in 1992 (39/37) and three degrees in 1996 (37/34).

On the cold side, in 1989 the high was 27 with a low of 10 (our most recent 10s low). The other low of 10 occurred in 1970. These lows of 10 degrees were O'Hare's coldest. In 1985 the high was 36 with a low of 13. The other cold low was 17 in 1981. The other cold highs were 32 in 1997 and 32 a decade later, in 2007. The record low of -1 was set in 1950 at Midway. The record coldest high of 19 occurred way back in 1893, at a time when the official readings were taken adjacent to Lake Michigan. 25 of the last 33 lows (76%) were in the: 20s (11) and 30s (14). Lows were in the 20s & 30s for: eight consecutive years from 1990 through 1997 and seven consecutive years from 2002 through 2008. Four lows (12%) were in the cold 10s (a.k.a. teens) and four more (12%) were in the warm 40s. The cold lows of the 10s (a.k.a. teens) occurred from 1989 and before while the warm 40s lows occurred from 1998 onward.

There was an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1997 the high was 32 with a low of 20, overall 11 degrees BELOW normal. Then in 1998 the high was 60 with a low of 40, overall 13 degrees ABOVE normal.

Three of four years from 1998-2001 were warm. In 1998, it was 13 degrees above normal (60/40). In 1999, it was 14.5 degrees above normal (63/40). Then 2000 was below normal (36/21). And 2001 was 14.5 degrees above normal (59/44).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:22 and sunrise is at 6:53. Sunset is at 16:26 and twilight ends at 16:57. There's a total of 9 hours, 33 minutes of daylight today and 10 hours, 35 minutes between twilights. We lost a minute of daylight from yesterday. Tomorrow twilight begins at 6:24 and sunrise is at 6:54. The moon is waning crescent, heading towards new in two days at 0:10. Illumination was 6% at midnight, will be 3% at noon and 2% at midnight tonight. Moonrise is at 4:57 this morning. Moonset is at 15:08 this afternoon. Moonrise is at 6:13 tomorrow morning. Moonlight time is 10 hours, 11 minutes which is 36 minutes shorter than yesterday.

Cool Fall began November 2 and runs for 29 days through November 30. High temperatures in this period are usually in the 30s, 40s and 50s. Highs in the 10s and 20s occur infrequently. Thanksgiving is tomorrow.