September 8: ORD

Today is September 8th. It's the 251st day of the year. 114 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 58. I've calculated the 32-year averages at 79 and 59.

On the hot side, in 1985 the high was 94 with a low of 67. Six years later, in 1991, the high was 88 with a low of 67. The other 90s highs were 92 in 2002 (our most recent) and 90 in 1983. The record high of 96 was last set in 1960 at Midway, after previously being set in 1959 (also at Midway) and originally in the city in 1933. Our most recent 70s low was 70 in 1964. The record warmest low of 76 occurred way back in 1922, a time when the official thermometer was located adjacent to Lake Michigan. 26 of the past 32 highs (81%) were in the: 70s (13) and 80s (13). Three highs were in the hot 90s and three 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 95 with a low of 68, a hot day. In 1976 the high was a hot 90 with a low of 57, a 33 degree spread. In 1971 the high was a hot 94 with a low of 69, a hot day. In 1967 the high was 83 with a low of 50, a 33 degree spread. In 1966 the high was 81 with a cold low of 44, a 37 degree spread. In 1965 the high was 67 with a low of 61, a six degree spread. In 1964 the high was 92 with a low of 70, a hot day. In 1960 the high was a hot 93 with a low of 69, a hot day and year of the record high of 96 at Midway. In 1959 the high was 97 (hotter than the record high) with a low of 71, a hot day.

More recently, there were large spreads of 38 degrees in 1983 (90/52) and 32 degrees in 2002 (92/60). There were no small spreads of up to seven degrees.

On the cool side, in 1986 the high was 73 with the record low of 43, a 30 degree spread. In 1979 the high was 66 with a low of 51. Another cold 40s low was 47 in 1982. The other cool 60s highs were 65 in 1995 and 67 three years ago (in 2008). The record coolest high of 54 occurred way back in 1883, a time when the official thermometer was located adjacent to Lake Michigan. 30 of the last 32 lows (94%) were in the: 50s (13) and 60s (17). Two lows were in the cold 40s. There's an ongoing, 24-year streak of 50s & 60s lows that began in 1987.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:57 and sunrise is at 6:26. Sunset is at 19:16 and twilight ends at 19:44. There's a total of 12 hours, 50 minutes of daylight today and 13 hours, 47 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:58 and sunrise is at 6:27. The moon is waxing gibbous, heading towards the full Harvest (a.k.a. Barley) moon in four days at 4:27. Illumination was 84% at midnight, will be 88% at noon and 91% at midnight tonight. Moonset is at 2:41 this morning. Moonrise is at 17:12 this afternoon. Moonset is at 3:44 tomorrow morning. Moonlight time is 9 hours, 29 minutes which is 32 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 three days.