October 27: ORD

Today is October 27th. It's the 300th day of the year. 65 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 58 and the normal low is 40. I've calculated the 32-year averages at 58 and 40.

On the warm side, in 1984 the high was 76 with the record warmest low of 63. In 1998 the high was 70 with a low of 56. In 1989 the high was 76 with a low of 49. In 2000 the high was 71 (our most recent 70s high) with a low of 51. The other warm lows were 53 in 2004 and 52 in 1996. The record high of 83 was set back in 1927, a time when the official readings were taken adjacent to Lake Michigan. 27 of the past 32 highs (84%) were in the: 40s (7), 50s (9) and 60s (11). The long consecutive streaks of highs in the 40s, 50s & 60s were: seven years from 1990 through 1996 and ten years from 2001 through last year, 2010. Four highs were in the warm 70s and one was in the cold 30s (O'Hare's only 30s high of 38 in 1997). There were three more 70s highs prior to 1979.

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 42 with a low of 23, a cold day. In 1974 the high was a warm 72 with a low of 38, a 34 degree spread. In 1971 the high was 74 with a low of 54, a warm day. In 1970 the high was 67 with a warm low of 60, a seven degree spread and warm day. In 1969 the high was 44 with a low of 28, a cold day. In 1967 the high was a cold 41 with a low of 34, a seven degree spread and cool day. In 1966 the high was a warm 70 degrees. In 1962 the high was 64 with a low of 34, a 30 degree spread. In 1961 the low was a cold 25 degrees. In 1959 the high was a cold 40 with a low of 33, a seven degree spread and cool day.

More recently, there were large spreads of 33 degrees in 1983 (65/32) and 32 degrees in 1982 (65/33). There were small spreads of six degrees in 1991 (53/47), six degrees two years ago, in 2009 (51/45), and seven degrees in 2006 (45/38).

On the cold side, in 1997 the high was 38 with a low of 26. In 1980 the high was 43 with a low of 27. In 2001 the high was 45 with a low of 30. The other cold highs were 44 in 2003, 45 in 2006, 46 in 1993 and 46 in 2002. The record low of 24 was set in 1942 at Midway. The record coldest high of 34 was set in 1925, a time when the official readings were taken adjacent to Lake Michigan. 25 of the last 32 lows (78%) were in the: 30s (16) and 40s (9). The long consecutive streaks of lows in the 30s and 40s were: 11 years from 1985 through 1995 and six years from 2005 through last year, 2010. Two lows were in the cold 20s. Five lows were in the warm: 50s (4) and 60s (1). Just one other low was in the 60s prior to 1979 (60 in 1970).

There's an instance of back-to-back years in which temperatures were just about as opposite as they can be. In 1997 the high was 38 with a low of 26, overall 17 degrees BELOW normal. Then in 1998 the high was 70 with a low of 56, overall 14 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 two minutes of daylight from yesterday. Tomorrow twilight begins at 6:52 and sunrise is at 7:21. The moon is waxing crescent, having passed new yesterday at 14:56. Illumination was 0% at midnight, will be 1% at noon and 3% at midnight tonight. Moonrise is at 8:27 this morning. Moonset is at 18:21 tonight. Moonrise is at 9:41 tomorrow morning. Moonlight time is 9 hours, 54 minutes which is 33 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. Halloween is in four days. Election Day is in 12 days.