September 2: ORD

Today is September 2nd. It's the 245th day of the year. 120 days remain. It's week 35 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 80 and the normal low is 60. I've calculated the 32-year averages at 80 and 59.

On the hot side, three years ago, in 2008, the high was 94 with a low of 65. In 2000 the high was 91 with a low of 67. In 1979 the high was 86 with a low of 70, our only 70s low. The other 90s high was 90 in 1999. The record high of 101 was set in 1953. The record warmest low of 78 was set back in 1913. 28 of the past 32 highs (88%) were in the: 70s (12) and 80s (16). Three highs were in the hot 90s. One high was in the cool 60s. Highs in the 70s & 80s occurred in 19 straight years from 1975 through 1993.

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 58 with a low of 48, a cool day. That high of 58 is colder than the record coolest high. In 1973 the high was 91 with a warm low of 73, a hot day. In 1972 the high was a cool 68 degrees. In 1967 the high was 73 with a cold low of 40, a 33 degree spread and cool day. That low of 40 was colder than the record low. In 1964 the high was 81 with a low of 49, a 32 degree spread. In 1962 the high was 82 with a low of 52, a 30 degree spread. In 1960 the low was a warm 72 degrees.

More recently, there were large spreads of 33 degrees in 1999 (90/57) and 30 degrees in 1983 (88/58). There were no small spreads (up to seven degrees).

On the cool side, in 1994 the high was 68 with a low of 49. In 1987 the high was 70 with a low of 51. Two years ago, in 2009, the high was 73 with a low of 50. Another low of 49 occurred in 2001. Even colder, the record low of 44 was set in 1946. The record coolest high of 61 occurred in 1974. Another cool high of 63 occurred back in 1935. 29 of the last 32 lows (91%) were in the: 50s (12) and 60s (17). Two lows were in the cold 40s and one was in the warm 70s. For 14 years, from 1980 through 1993, lows were in the 50s & 60s. For nine years, from 2002 through 2010, lows were in the 50s & 60s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:51 and sunrise is at 6:19. Sunset is at 19:26 and twilight ends at 19:55. There's a total of 13 hours, 7 minutes of daylight today and 14 hours, 4 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:52 and sunrise is at 6:20. The moon is waxing crescent. Illumination was 23% at midnight, will be 28% at noon and 34% at midnight tonight. Moonrise is at noon today. Moonset is at 21:52 tonight. Moonrise is at 13:11 tomorrow afternoon. Moonlight time is 9 hours, 52 minutes which is 34 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 three days. 9/11 Remembrance Day and Grandparents Day are in eight days.