November 29: ORD

Today is November 29th. It's the 333rd day of the year. 32 days remain. It's week 48 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 41 and the normal low is 26. I've calculated the 33-year averages at 42 and 28.

On the warm side, in 1998 the high was the record high of 68 with the record warmest low of 57 (our only 50s low). In 1991 the high was 60 with a low of 38. In 2006 the high was 60 with a low of 38. In 1997 the high was 49 with a low of 42 (our only 40s low), a seven degree spread. The other warm low was 39 in 2001. 29 of the past 33 highs (88%) were in the: 30s (15) and 40s (14). There were consecutive streaks of highs in the 30s & 40s as follows: 1. 11 from 1978 through 1988, 2. six from 1992 through 1997 and 3. seven from 1999 through 2005. Three highs were in the warm 60s. The only pre-1978 high of 60 or more at ORD was 62 in 1975. One high was in the cold 20s. There have been no highs in the 50s over the past 33 years. ORD's only 50s high for the date was 59 in 1962.

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 33 with a cold low of 8, a cold day. In 1976 the high was 13 with a low of 1, a cold day. In 1975 the high was a warm 62 with a low of 37, a warm day. In 1971 the high was 40 with a low of 33, a seven degree spread. In 1970 the low was a warm 39 degrees. In 1968 the high was 36 with a low of 31, a five degree spread. In 1964 the high was 18 with a low of 9, a cold day. In 1962 the high was a warm 59 with a low of 25, a 34 degree spread. In 1960 the high was a cold 28 with a low of 21, a seven degree spread. Also in 1960, there was a rare 44 degree drop in temperature from the high of 63 on the 28th to a low of 19 on the 30th. In 1959 the high was 28 with a low of 7, a cold day. In 1958 the high was 22 with a low of 3, a cold day.

More recently, there were no large spreads. There were small spreads of three degrees in 1982 (40/37), five degrees in 2000 (37/32), six degrees in 2001 (45/39), six degrees in 2004 (38/32) and seven degrees in 1983 (31/24).

On the cold side, in 1989 the high was 29 (our only 20s high) with a low of 12. In 1995 the high was 33 with a low of 11. The record low of -2 was set way back in 1872. The record coldest high of 10 was set back in 1929. Both records were established at a time when the official readings were taken adjacent to Lake Michigan. 27 of the last 33 lows (82%) were in the: 20s (16) and 30s (11). There were two stretches of 20s & 30s lows: 1. seven years from 1982 through 1988 and 2. eight years from 1999 through 2006. Four lows were in the cold 10s (a.k.a. teens). Our most recent 10s low was 18 in 2007. Two lows were in the warmer: 40s (1) and 50s (1). Those warm lows occurred in back-to-back years (42 in 1997 and 57 in 1998 (the record warmest low)).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:29 and sunrise is at 7:00. Sunset is at 16:23 and twilight ends at 16:54. There's a total of 9 hours, 23 minutes of daylight today and 10 hours, 25 minutes between twilights. We lost a minute of daylight from yesterday. Tomorrow twilight begins at 6:30 and sunrise is at 7:01. The moon is waxing crescent. Illumination was 20% at midnight, will be 24% at noon and 29% at midnight tonight. Moonrise is at 10:44 this morning. Moonset is at 21:18 tonight. Moonrise is at 11:15 tomorrow morning. Moonlight time is 10 hours, 34 minutes which is 30 minutes longer 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. Pearl Harbor Day is in eight days. Bill of Rights Day is in 16 days.