September 9: ORD

Today is September 9th. It's the 252nd day of the year. 113 days remain. It's week 36 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 78 and the normal low is 57. I've calculated the 32-year averages at 78 and 57.

On the hot side, in 1983 the high was the record high of 95 with a low of 70. That record high of 95 also occurred in 1959 and originally four years before in 1955. In 1991 the high was 94 with a low of 70 (our most recent 70s low). In 2002 the high was 90 (our most recent 90s high) with a low of 66. The record warmest low of 75 occurred way back in 1912, a time when the thermometer was located adjacent to Lake Michigan. 25 of the past 32 highs (78%) were in the: 70s (15) and 80s (10). Three highs were in the hot 90s. Four highs were in the cool 60s.

In looking back through the years to the first September at O'Hare in 1959, the following instances were notable: in 1978 the high was a hot 93 with a low of 65, a hot day. In 1971 the high was 90 with a low of 69, a hot day. In 1966 the high was 82 with a cold low of 45, a 37 degree spread. In 1964 the high was a hot 94 with a low of 62, a 32 degree spread. In 1963 the high was 85 with a low of 54, a 31 degree spread. In 1959 the high was a hot 90 degrees.

More recently, there were large spreads of 34 degrees in 1982 (81/47), 31 degrees in 1988 (81/50) and 30 degrees in 1981 (75/45). There was a small spread of seven degrees in 2006 (70/63).

On the cool side, in 1986 the high was 73 with the record low of 43, a 30 degree spread. Last year, in 2010, the high was 67 with a low of 50. In 1995 the high was 69 with a low of 48. Three years ago, in 2008, the high was 69 with a low of 49. The only other 60s high was 67 in 1992. The other cold 40s lows were 45 in 1981, 47 in 1982 and 48 in 1979. The record coolest high of 56 occurred way back in 1883, a time when the thermometer was located adjacent to Lake Michigan. 24 of the last 32 lows (75%) were in the: 50s (12) and 60s (12). Six lows were in the cold 40s and two were in the warm 70s. For 12 consecutive years, from 1996 through 2007, lows were in the 50s & 60s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:58 and sunrise is at 6:27. Sunset is at 19:14 and twilight ends at 19:42. There's a total of 12 hours, 47 minutes of daylight today and 13 hours, 44 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:59 and sunrise is at 6:28. The moon is waxing gibbous, heading towards the full Harvest (a.k.a. Barley) moon in three days at 4:27. Illumination was 91% at midnight, will be 93% at noon and 96% at midnight tonight. Moonset is at 3:44 this morning. Moonrise is at 17:41 this afternoon. Moonset is at 4:47 tomorrow morning. Moonlight time is 10 hours, 3 minutes which is 34 minutes longer than yesterday.

Summer began June 4 and runs for 110 days through September 21. High temperatures in this period are usually in the 70s and 80s. Highs in the 60s, 90s and 100s occur infrequently. 9/11 Remembrance Day and Grandparents Day are in two days.