September 15: ORD

Today is September 15th. It's the 259th day of the year. 107 days remain. It's week 38 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. Observations have been official at O'Hare since Thursday, January 17, 1980.

According to the National Climatic Data Center (NCDC), the normal high is 74 and the normal low is 54. The 29-year averages are 72 and 54.

On the hot side, in 1994 the high was 91 with a low of 71. In 1991 the high was 91 with a low of 68. In 2004 the high was 86 with a low of 68. In 1992 the high was 85 with a low of 68. In 1987 the high was 81 with a low of 64. Other warm highs were 82 in 1997 and 80 in 1986. Another warm low was 67 in 1998. 4 of the 8 years from 1987 to 1994 comprised 4 of the 5 warmest days. The record high of 99 was set in 1939 and the record warmest low of 75 was set in 1927. 21 of the 29 highs have been 60s (10) and 70s (11).

The biggest difference between a daily high and low was 31 degrees in 1985 (high of 71, low of 40). One small difference was five degrees in 1998 (high of 72, low of 67). The other small difference is listed below on the cool side.

On the cool side, last year the high was 61 with the record low of 39 (the former record low was 40 in 1985). In 1984 the high was 62 with a low of 41. In 1993 the high was 55 (the earliest 50s high of fall and record-tying coolest high) with a low of 51 (just a 4 degree difference between the high and low). The other cool lows were 40 in 1985, 43 in 1999, 47 (1979, 1989) and 49 in 2000. The other record coolest high of 55 was set in 1916. 16 of the 29 lows since 1979 have been 50s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:06 and sunrise is at 6:34. Sunset is at 19:02 and twilight ends at 19:30. Twilight begins tomorrow at 6:07 and sunrise is at 6:35. There's a total of 12 hours, 28 minutes of daylight today and 13 hours, 24 minutes between twilights. The moon reached full Harvest today at 4:13. Illumination was 100% at midnight, will be 100% at noon and 99% at midnight tonight. Moonset is at 6:50 this morning. Moonrise is at 18:58 tonight and moonset is at 8:02 tomorrow. Moonlight time is 11 hours, 52 minutes today.

Constitution Day, also known as Citizenship day, is in two days. This is a newer holiday, having been enacted by Congress just four years ago. The website "www.patriotism.org" says that Constitution Day is "a birthday for our country and it serves as a means for American citizens to express their pride in their citizenship. Constitution Day also designates a time to honor the Constitution of America and learn more about the famous piece of legislation." -Bernie-