October 23: ORD

Today is October 23rd. It's the 296th day of the year. 69 days remain. It's week 43 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 60 and the normal low is 41. I've calculated the 32-year averages at 59 and 42.

On the warm side, in 1992 the high was 76 with a low of 58. The year before, in 1991, the high was 77 with a low of 55. In 2004 the high was 76 (our most recent 70s high) with a low of 55. In 2000 the high was 71 with a low of 58. The next year, 2001, the high was 65 with a low of 58, a seven degree spread. The other warm highs were 72 in 1989 and 71 in 1995. The other warm lows were 55 in 1986, 54 in 1985 and 54 last year, in 2010. The record high of 85 was set in 1963 at Midway. The record warmest low of 64 occurred back in 1920, a time when the official readings were taken adjacent to Lake Michigan. 25 of the past 32 highs (78%) were in the: 40s (7), 50s (9) and 60s (9). Six highs were in the warm 70s and one was in the cold 30s.

In looking back through the years to the first October at O'Hare in 1959, the following instances were notable: in 1975 the high was 78 with a low of 60, a warm day. In 1973 the high was a warm 75 with a low of 45, a 30 degree spread. In 1971 the high was 62 with a warm low of 57, a five degree spread. In 1970 the low was a warm 54 degrees. In 1969 the high was 48 with a low of 25, a cold day. In 1967 the high was 78 with a low of 54, a warm day. In 1964 the high was 53 with a cold low of 22 degrees, a 31 degree spread and a cool day. In 1963 the high was 85 with a low of 55, a 30 degree spread, a hot day and year of the record high, also of 85 at Midway. In 1963, 4 of 5 days from the 22nd to the 26th, highs were in the 80s. In 1962 the high was 47 with a low of 29, a cold day.

More recently, there were large spreads of 30 degrees in 1989 (72/42) and 30 degrees in 1993 (68/38). There was a small spread of five degrees in 1983 (52/47), six degrees in 1979 (45/39) and six degrees in 2002 (46/40).

On the cold side, in 1981 the high was the record coldest high of 35 (O'Hare's only 30s high for the date) with the record low of 20. The next year, 1982, the high was 54 with a low of 23. The other cold lows were 28 in 1984 and 29 in 1987. The other cold highs were 45 in 1979, 46 in 2002, 48 in 1996 and 48 in 2005. 28 of the last 32 lows (88%) were in the: 30s (10), 40s (10) and 50s (8). Four lows were in the cold 20s. These 20s lows occurred within a span of seven years from 1981 to 1987. Additionally, there were three other 20s lows prior to 1979.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:47 and sunrise is at 7:15. Sunset is at 18:00 and twilight ends at 18:28. There's a total of 10 hours, 45 minutes of daylight today and 11 hours, 41 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 6:48 and sunrise is at 7:16. The moon is waning crescent. Illumination was 18% at midnight, will be 14% at noon and 10% at midnight tonight. Moonrise is at 3:19 this morning. Moonset is at 15:53 this afternoon. Moonrise is at 4:33 tomorrow morning. Moonlight time is 12 hours, 34 minutes which is 43 minutes shorter than yesterday.

Warm Fall began September 22 and runs for 41 days through November 1. High temperatures in this period are usually in the 50s, 60s and 70s. Highs in the 30s and 40s occur infrequently. United Nations Day is tomorrow.