September 3: ORD

Today is September 3rd. It's the 246th day of the year. 119 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 79 and the normal low is 60. I've calculated the 32-year averages at 80 and 59.

On the hot side, in 1985 the high was 88 with a low of 72. In 2000 the high was 85 with a low of 69. In 2007 the high was 88 with a low of 66. The 90s highs were 91 in 1983 and 90 in 1999. The record high of 97 was set in 1953. The record warmest low of 75 occurred in 1973. 27 of the past 32 highs (84%) were in the: 70s (11) and 80s (16). Two highs were in the hot 90s and three were in the cool 60s. There were two long stretches of highs in the 70s & 80s. The first was ten years from 1984 through 1993. The second was 11 years from 2000 through last year, 2010 (ongoing).

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 64 with a low of 46, a cool day. That low of 46 was colder than the record low of 47 and 1974 is the year of the record low. In 1973 the high was a hot 92 with a low of 70, a hot day. 1973 is the year of the record warmest low of 73. In 1971 the low was a warm 73 degrees. In 1967 the high was 76 with a cold low of 44, a 32 degree spread. That low of 44 was colder than the record low. In 1964 the high was a hot 94 with a low of 67, a hot day. In 1960 the high was 96 with a low of 72, a hot day.

More recently, there was a large spread of 31 degrees in 1983 (91/60). There was a small spread of six degrees in 1981 (66/60).

On the cool side, in 1997 the high was 67 with a low of 50. A decade earlier, in 1987, the high was 72 with a low of 49. Three years prior, in 1984, the high was 71 with a low of 51. Two years before, in 1982, the high was 74 with a low of 48. The other 60s highs were 66 in 1981 and 68 in 1994. The record low of 47 was set in 1974. The record coolest high of 59 occurred way back in 1891. 29 of the last 32 lows (91%) were in the: 50s (14) and 60s (15). Two lows were in the cold 40s and one was in the warm 70s (72 in 1985). There's an ongoing, long period of lows in the 50s and 60s. This 23-year period started in 1988 and is still going as of last year (2010).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:52 and sunrise is at 6:20. Sunset is at 19:24 and twilight ends at 19:53. There's a total of 13 hours, 4 minutes of daylight today and 14 hours, 1 minute between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:53 and sunrise is at 6:22. The moon is waxing crescent and reaches first quarter tomorrow at 12:39. Illumination was 34% at midnight, will be 39% at noon and 45% at midnight tonight. Moonrise is at 13:11 this afternoon. Moonset is at 22:40 tonight. Moonrise is at 14:15 tomorrow afternoon. Moonlight time is 9 hours, 29 minutes which is 23 minutes shorter 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. Labor Day is in two days. 9/11 Remembrance Day and Grandparents Day are in eight days.