September 27: ORD

Today is September 27th. It's the 270th day of the year. 95 days remain. It's week 39 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.

According to the National Climatic Data Center (NCDC), the normal high is 70 and the normal low is 49. I've calculated the 31-year averages at 72 and 50.

On the warm side, in 1986 the high was 86 with a low of 68. The year later, 1987, the high was 89 with a low of 61. In 1998 the high was 86 with a low of 60. Other warm highs were 84 in 1990 and 83 in 1979. The record high of 91 and record warmest low of 71 were set on the same day in 1971. Over the last 31 years, 27 highs (87%) were: 60s (11) and 70s (8) and 80s (8). Four highs were in the cooler 50s.

In looking back through the years to the first September at O'Hare in 1959, the following instances were notable: in 1975 the high was 70 with a low of 40, a 30 degree spread. In 1973 the high was 80 with a low of 63, a warm day. In 1971 the high was 86 with a low of 69, a hot day. In 1967 the high was a cool 55. In 1964 the high was 61 with a low of 35, a cool day. In 1963 the high was a warm 85 with a low of 52, a 33 degree spread. In 1961 the high was 71 with a low of 40, a 31 degree spread. The last sub-60 degree high occurred 16 years ago in 1994 (58 degrees).

More recently, there were large spreads of 37 degrees in 1990 (84/47), 31 degrees in 1985 (68/37), 31 degrees in 2004 (76/45) and 30 degrees in 1983 (79/49). There were small spreads of seven degrees in 1993 (53/46) and 1994 (58/51).

On the cool side, in 1984 the high was the near-record coolest high of 50 (the record is 49, set in 1942) with a low of 36. In 1991 the high was 58 with a low of 34. Other cool highs were 53 in 1993 and 58 in 1994. Other cool lows were 37 in both 1985 and 1989. There have been no lows below 45 for the last 18 years (since 34 degrees in 1991). The record low of 31 was set in 1942. 23 of the last 31 lows (74%) were: 40s (13) and 50s (10). Four lows were in the cooler 30s and four lows were in the warmer 60s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:18 and sunrise is at 6:46. Sunset is at 18:42 and twilight ends at 19:10. There's a total of 11 hours, 56 minutes of daylight today and 12 hours, 52 minutes between twilights. We are losing two or three minutes of daylight a day. Tomorrow twilight begins at 6:19 and sunrise is at 6:47. The moon is waning gibbous. Illumination was 86% at midnight, will be 83% at noon and 79% at midnight tonight. Moonset is at 11:10 this morning. Moonrise is at 20:36 tonight. Moonset is at 12:12 tomorrow afternoon. Moonlight time is 14 hours, 34 minutes which is 26 minutes longer than yesterday.

Columbus Day is in 14 days. -Bernie-