October 26: ORD

Today is October 26th. It's the 300th day of the year. 66 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. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. Before this, 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 58 and the normal low is 40. I've calculated the 33-year averages at 57 and 41.

On the warm side, in 2000 (tied with 1971 as O'Hare's warmest October 26th) the high was 76 (O'Hare's third hottest high of the date) with a low of 59 (O'Hare's warmest low of the date). In 1989 the high was 75 with a low of 50. In 1996 the high was 68 with a low of 56 (O'Hare's third warmest low of the date). Two years ago, in 2010, the high was 70 (occurred early in the morning) with a low of 54. In 1998 the high was 73 with a low of 50. The other warm highs were 72 degrees in 1964 and 70 degrees in 1985. The other warm lows were 53 degrees in 2004, 53 degrees in 2007 and 52 degrees in 1986. The record high of 84 degrees was set in 1963 at Midway. The record warmest low of 63 degrees was set back in 1939 at the University of Chicago. 21 of the past 33 highs (64%) were in the: 50s (13) and 60s (8). There were seven consecutive highs in the 50s and 60s from 1990 through 1996. Our most recent 60s high was 60 degrees in 2004. Five highs (15%) were in the warm 70s. Seven highs (21%) were in the cold 40s. Three consecutive years had highs in the 40s: 41 degrees in 2001, 47 degrees in 2002 and 45 degrees in 2003. 1971 is tied with 2000 as O'Hare's warmest October 26th. In 1971 the high was 78 (O'Hare's second hottest high of the date) and low of 57 (O'Hare's second warmest low of the date). O'Hare's second warmest 10/26 was in 1963 as the high was 83 (O'Hare's hottest and only 80s high of the date) with a low of 45. The other warm day was in 1970 (high of 72, low of 52).

In looking back through the years to the first October at O'Hare in 1959, the following instances were notable: in 1974 the high was 66 with a low of 34, a 32 degree spread. In 1971 the high was 78 with a low of 57, a warm day. In 1970 the high was 72 with a low of 52, a warm day. In 1966 the high was 62 with a cold low of 25, a 37 degree spread. In 1964 the high was a warm 72 degrees. In 1963 the high was a warm 83 with a low of 45, a 38 degree spread, warm day and year of the record high of 84 at Midway. In 1962 the high was 45 with a low of 19 (colder than the record low of 22), a cold day. In 1961 the low was a cold 28 degrees. In 1959 the high was a cold 39 with a low of 34, a five degree spread and cold day.

More recently, there was a large spread of 33 degrees in 1982 (64/31). There were small spreads of three degrees in 2006 (46/43), five degrees in 2001 (41/36), six degrees three years ago, in 2009 (55/49), seven degrees in 1986 (59/52), seven degrees in 1991 (54/47) and seven degrees in 2004 (60/53).

On the cool side, in 1980 (O'Hare's second coolest October 26th) the high was 42 (O'Hare's third coolest high of the date) with a low of 26 (O'Hare's third coldest low of the date). In 1988 the high was 44 with a low of 28. The other cool highs were 41 degrees in 2001 (O'Hare's second coolest high of the date), 45 degrees in 2003, 46 degrees in 1997 and 46 degrees in 2006. The other cold lows were 25 degrees in 1966 (O'Hare' second coldest low of the date), 27 degrees in 1979, 28 degrees in 1961 and 28 degrees in 1990. The record low of 22 degrees and record coolest high of 37 degrees were set on the same cold day back in 1942 at Midway. That record low of 22 degrees was originally set way back in 1887. 13 of the last 33 lows (39%) were in the 30s. Some of the 30s lows occurred in two streaks: 1. 33 degrees in 1981, 31 degrees in 1982 and 32 degrees in 1983 and 2. 36 degrees in 2001, 38 degrees in 2002 and 35 degrees in 2003.  Four lows (12%) were in the cold 20s. The 20s lows occurred in two clusters: 1. 27 and 26 degrees in 1979 and 1980 and 2. 28 degrees in both 1988 and 1990 (our most recent 20s low). 16 lows (49%) were in the warm: 40s (8) and 50s (8). O'Hare's coolest October 26th was in 1962 as the high was 45 with a low of 19 (O'Hare's coldest low of the date and a low that's colder than the record low). The other cool day was in 1959 as the high was 39 (O'Hare's coolest high of the date) and low of 34.

There's an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1988 the high was 44 with a low of 28, overall 13 degrees BELOW normal. Then in 1989 the high was 75 with a low of 50, overall 13.5 degrees ABOVE normal.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:51 and sunrise is at 7:20. Sunset is at 17:54 and twilight ends at 18:23. There's a total of 10 hours, 34 minutes of daylight today and 11 hours, 32 minutes between twilights. We lost four minutes of daylight from yesterday. Tomorrow twilight begins at 6:52 and sunrise is at 7:21. The moon is waxing gibbous, heading towards the full Hunter's moon in three days at 14:49. Illumination was 88% at midnight, will be 91% at noon and 94% at midnight tonight. Moonset was at 4:13 this morning. Moonrise is at 16:12 this afternoon. Moonset is at 5:14 tomorrow morning. Moonlight time is 12 hours, 1 minute which is 36 minutes longer than yesterday.

Warm Fall began September 22nd and runs for 41 days through November 1st. High temperatures in this period are usually in the 50s, 60s and 70s. Highs in the 30s and 40s occur infrequently. Halloween is in five days. Standard Time returns in nine days. Election Day is in 11 days.