October 12: ORD

Today is October 12th. It's the 286th day of the year. 80 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 64 and the normal low is 44. I've calculated the 33-year averages at 65 and 44.

On the warm side, in 2008 (O'Hare's warmest October 12th) the high was the record-tying high of 84 with a low of 57. The other record highs of 84 occurred in 1956 and 1960. In 1997 (O'Hare's second warmest October 12th) the high was 82 with a low of 58 (O'Hare's second warmest low of the date). Two years earlier, in 1995, the high was 83 (O'Hare's second hottest high of the date) with a low of 55. Last year, in 2011, the high was 78 with a low of 55. The record warmest low of 67 degrees occurred back in 1928 at the University of Chicago. 27 of the past 33 highs (82%) were in the: 50s (6), 60s (11) and 70s (10). Three highs were in the warm 80s. Three highs were in the cold: 30s (1) and 40s (2). In 2006 the lone 30s high of 39 degrees occurred. 2006 was also the year of the earliest measurable snowfall. An inch fell here in Crystal Lake and in neighboring Algonquin. An inch and a half fell at Arlington Heights. Both O'Hare and Midway airports received three tenths of an inch. The suburb of DeKalb had half an inch. October 12, 2006 beat October 18 in 1972 and 1989, the previous earliest dates for snow. O'Hare's other warm highs of the date are 78 degrees in 1961 and 76 degrees in: 1962, 1975, 1985 and 2010. O'Hare's other warm days were in: 1960 with a high of 82 and low of 53, 1973 with a high of 74 and low of 61 (O'Hare's warmest low of the date) and 1976 with a high of 79 and low of 57.

In looking back through the years to the first October at O'Hare in 1959, the following instances were notable: in 1976 the high was 79 with a low of 57, a warm day. In 1975 the high was a warm 76 with a low of 41, a 35 degree spread. In 1973 the high was 74 with a warm low of 61, a warm day. In 1971 the high was 70 with a low of 39, a 31 degree spread. In 1969 the high was 61 with a low of 54, a seven degree spread. In 1968 the high was 75 with a low of 44, a 31 degree spread. In 1967 the high was 63 with a cold low of 28, a 35 degree spread. In 1966 the high was 65 with a cold low of 31, a 34 degree spread. In 1962 the high was a warm 76 degrees. In 1961 the high was a warm 78 with a low of 45, a 33 degree spread. In 1960 the high was a warm 82 with a low of 53, a warm day. 1960 was also the year of the co-record high of 84 at Midway. In 1959 the low was a cold 32 degrees.

More recently, there were large spreads of 32 degrees in 1990 (64/32), 32 degrees in 1994 (67/35), 31 degrees in 1987 (59/28) and 30 degrees in 2000 (73/43). There was a small spread of seven degrees two years ago, in 2009 (48/41).

On the cool side, in 2006 (O'Hare's coolest October 12th) the high was 39 (O'Hare's coolest high of the date) with a low of 30 (O'Hare's second coldest low of the date). In 1988 (O'Hare's second coolest October 12th) the high was 48 (O'Hare's co-second coolest high of the date with 2009) with the co-record low of 28. In 1980 the high was 53 with a low of 31.  The other cold lows were the co-record low of 28 degrees in: 1967 and 1987, 31 degrees in 1966 and 32 degrees in: 1959 and 1990. The record coolest high of 38 degrees occurred back in 1917, a time when the official readings were taken adjacent to Lake Michigan. O'Hare's other cool highs are 48 degrees in 2009 (O'Hare's other co-second coolest high of the date with 1988) and 51 degrees in 1979 (O'Hare's third coolest high of the date). 31 of the last 33 lows (94%) were in the: 30s (8), 40s (13) and 50s (10). Two lows were in the cold 20s. The 20s lows were 28 degrees and they occurred in the back-to-back years of 1987 and 1988.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:35 and sunrise is at 7:03. Sunset is at 18:15 and twilight ends at 18:44. There's a total of 11 hours, 12 minutes of daylight today and 12 hours, 9 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 6:36 and sunrise is at 7:04. The moon is waning crescent. Illumination was 14% at midnight, will be 10% at noon and 7% at midnight tonight. Moonrise was at 3:44 this morning. Moonset is at 16:27 this afternoon. Moonrise is at 4:53 tomorrow morning. Moonlight time is 12 hours, 43 minutes which is 37 minutes shorter 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. United Nations Day is in 12 days. Standard Time doesn't return until November 4th.