September 6: ORD

Today is September 6th. It's the 249th day of the year. 116 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 59. I've calculated the 32-year averages at 80 and 59.

On the hot side, in 1990 the high was 96 with a low of 71. In 1985 the high was 93 with a low of 73. In 1998 the high was 92 (our most recent 90s high) with a low of 70. The record high of 97 was set in 1960 after originally being set six years earlier in 1954. The record warmest low of 78 occurred way back in 1881, a time when the thermometer was located adjacent to Lake Michigan. Another warm low was 73 in 2007. 25 of the past 32 highs (78%) were in the: 70s (10) and 80s (15). Three highs were in the hot 90s. Four highs were in the cool 60s, most recently 68 in 1993. For 12 straight years (ongoing) from 1999 through last year (2010) highs were in the 70s & 80s.

In looking back through the years to the first September at O'Hare in 1959, the following instances were notable: in 1976 the high was 83 with a cold low of 47, a 36 degree spread. In 1974 the low was a cold 46 degrees. In 1970 the high was 74 with a low of 67, a seven degree spread with 1.48 inches of rain. In 1969 the high was 78 with a warm low of 71, a seven degree spread with 1.32 inches of rain. In 1967 the high was 78 with a cold low of 45, a 33 degree spread. In 1963 the high was 77 with a cold low of 43, a 34 degree spread. In 1962 the low was a cold 43 degrees. In 1960 the high was 95 with a low of 71, a hot day. 1960 was the year of the record high of 97 degrees at Midway. In 1959 the high was a hot 92 with a low of 69, a hot day.

More recently, there were large spreads of 31 degrees in 1991 (85/54) and 31 degrees in 2003 (81/50). There was a small spread of seven degrees in 1989 (75/68).

On the cool side, in 1988 as the high was 66 with a low of 43. Four years earlier, in 1984, the high was 73 with the record low of 42. Two years later, in 1986, the high was 67 with a low of 49. Other cool 60s highs were 68 in 1982 and 68 in 1993. The other cold 40s low (our most recent) was 47 in 2000. The record coolest high of 61 occurred way back in 1885, a time when the thermometer was located adjacent to Lake Michigan. 24 of the last 32 lows (75%) were in the: 50s (13) and 60s (11). Four lows were in the cold 40s and four were in the warm 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:55 and sunrise is at 6:24. Sunset is at 19:19 and twilight ends at 19:48. There's a total of 12 hours, 55 minutes of daylight today and 13 hours, 53 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:56 and sunrise is at 6:25. The moon is waxing gibbous and reached first quarter two days ago at 12:39. Illumination was 66% at midnight, will be 71% at noon and 76% at midnight tonight. Moonset is at 0:33 this morning. Moonrise is at 15:59 this afternoon. Moonset is at 1:36 tomorrow morning. Moonlight time is 8 hours, 34 minutes which is 15 minutes shorter than yesterday. Moonlight time is at it's least today.

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 five days.