October 8: ORD

Today is October 8th. It's the 282nd day of the year. 84 days remain. It's week 41 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 of record 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 66 and the normal low is 45. I've calculated the 32-year averages at 66 and 46.

On the warm side, in 1997 (O'Hare's warmest October 8th) the high was the record high of 88 with a low of 62 (O'Hare's second warmest low of the date). A decade later, in 2007 (O'Hare's second warmest October 8th), the high was 87 (O'Hare's second hottest high of the date) with a low of 60. The high was also 87 degrees in 1949 at Midway. Last year, in 2011, the high was 82 with a low of 54. In 1984 the high was 76 with a low of 57. The record warmest low of 68 degrees occurred in 1939 at the University of Chicago. 28 of the past 33 highs (85%) were in the: 50s (7), 60s (11) and 70s (10). Four highs were in the warm 80s, all occurring more recently, in 1997, 2003, 2007 and 2011. One high was in the cool 40s. Seven of the ten 70s highs occurred between 1980 and 1993. Then there was a decade long 70s drought between 1994 and 2003. Then three 70s highs occurred from 2004 through 2010. O'Hare's warmest low of 63 degrees occurred in 1970. O'Hare's other warm highs are 80 degrees in 1966, 80 degrees in 2003, 79 degrees in 2010 and 78 degrees in 1993. The other warm lows were 57 degrees in both 1999 and 2004. 

In looking back through the years to the first October at O'Hare in 1959, the following instances were notable: in 1978 the low was a cold 31 degrees. In 1974 the high was 67 with a low of 35, a 32 degree spread. In 1970 the high was 67 with a warm low of 63, a four degree spread. In 1966 the high was a warm 80 with a low of 55, a warm day. In 1963 the high was 75 with a low of 41, a 34 degree spread. In 1961 the high was 76 with a low of 46, a 30 degree spread.

More recently, there were large spreads of 35 degrees in 1982 (75/40), 32 degrees in 2003 (80/48), 31 degrees last year, in 2010 (79/48) and 30 degrees in 1993 (78/48). There were small spreads of six degrees in 1990 (53/47) and seven degrees in 1999 (64/57).

On the cool side, in 2000 (O'Hare's coolest October 8th) the high was 46 (O'Hare's coolest high of the date) with a low of 31 (with 1978, O'Hare's second coldest low of the date). In 1987 (O'Hare's second coolest October 8th) the high was 56 with the record low of 27. The other cool highs were 50 degrees in 1996 (O'Hare's second coolest high of the date), 53 degrees in: 1990, 2005 and three years ago, in 2009. The record coolest high stands at 41 degrees, occurring way back in 1895 at a time when the official readings were taken adjacent to Lake Michigan. 20 of the last 33 lows (61%) were in the 40s. Four lows (12%) were in the cold: 20s (1) and 30s (3). Nine lows (27%) were in the warm: 50s (7) and 60s (2).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:31 and sunrise is at 6:59. Sunset is at 18:22 and twilight ends at 18:50. There's a total of 11 hours, 23 minutes of daylight today and 12 hours, 19 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 6:32 and sunrise is at 7:00. The moon reached last quarter at 2:33. Illumination was 51% at midnight, will be 46% at noon and 41% at midnight tonight. Moonset is at 14:18 this afternoon. Moonrise is at 0:30 tomorrow morning. Moonset is at 14:53 tomorrow afternoon. Moonlight time is 14 hours, 18 minutes which is 10 minutes longer than yesterday. Moonlight time is at its peak today.

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. Columbus Day is today. Standard Time doesn't return until November 4th.