September 17: ORD

Today is September 17th. It's the 260th day of the year. 105 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. 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 73 and the normal low is 54. I've calculated the 31-year averages at 73 and 53.

On the hot side, in 1988 the high was 90 with a low of 67. Another warm low was 66 in 1992. The record high of 93 was set in 1955. The record warmest low of 71 occurred back in 1906, a time when the official thermometer was located near the lakefront. Over the last 31 years, 23 highs (74% or about 3 of 4) were: 60s (9) and 70s (14). Seven highs were in the warmer: 80s (6) and 90s (1). One high was in the cooler 50s. Recently we had three consecutive years of 80s highs: 2006 (82), 2007 (80) and 2008 (82).

In looking back through the years to the first September at O'Hare in 1959, the following instances were notable: in 1974 the high was 83 with a low of 50, a 33 degree spread. In 1973 the high was a cool 60. In 1968 the high was 73 with a warm low of 67, a six degree spread. In 1965 the high was a hot 88. In 1964 the high was 84 with a low of 49, a 35 degree spread. In 1963 the high was a hot 87. In 1961 the high was 75 with a low of 44, a 31 degree spread. In 1959 the high was a cool 61 with a low of 44, a cool day.

More recently, there was a large spread of 32 degrees in 1984 (69/37).

On the cool side, in 1981 the high was the record coolest high of 51 with a low of 46, a five degree spread. The record low of 37 was set in 1984. Over the last 31 years, 21 lows (68% or 17 of 25) were 50s. Seven lows were in the cooler: 30s (1) and 40s (6). Three lows were in the warmer 60s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 6:07 and sunrise is at 6:35. Sunset is at 18:59 and twilight ends at 19:27. There's a total of 12 hours, 24 minutes of daylight today and 13 hours, 20 minutes between twilights. We are losing two or three minutes of daylight a day. Tomorrow twilight begins at 6:08 and sunrise is at 6:36. The moon is waxing gibbous. Illumination was 70% at midnight, will be 74% at noon and 78% at midnight tonight. Moonset was at 58 minutes past midnight. Moonrise is at 16:09 this afternoon. Moonset is at 2:00 tomorrow morning. Moonlight time is 8 hours, 49 minutes which is 23 minutes longer than yesterday.

Citizenship day is today and Columbus Day is in 24 days. -Bernie-