August 5: ORD

Today is August 5th. It's the 217th day of the year. 148 days remain. It's week 31 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 83 and the normal low is 64. I've calculated the 32-year averages at 81 and 63.

On the hot side, in 1996 the high was 90 with a low of 73. In 1980 the high was 87 with a low of 70. The other 90s high was 91 in 1984. The other 70s low was 71 in 1998. The record high of 102 was set back in 1918. The record warmest low of 78 was set way back in 1881. For both records, the thermometer was located near Lake Michigan. 19 of the past 32 highs (59%) were in the 80s. Two highs (7%) were in the hot 90s. 11 highs (34%) were in the cool: 60s (1) and 70s (10). Long stretches of highs under 90 characterize this day. For 11 years from 1985 through 1995 there were no 90s. For 14 years, still ongoing, from 1997 through 2010, there have been no highs in the 90s.

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1978 the low was a cool 50 degrees, a reading colder than the record low. In 1974 and 1972 the lows were 51, equal to the record low. In 1966 the high was 82 with a cool low of 52, a 30 degree spread. In 1962 the high was 85 with a low of 54, a 31 degree spread.

More recently, there were no large spreads of at least 30 degrees or small spreads of up to seven degrees.

On the cool side, in 1994 the high was 68 (the coolest high of the past 32 years) with the record low of 51. Three years later, in 1997, the high was 73 with a low of 53. Five years before that, in 1992, the high was also 73 with a low of 53. Another cool low was 52 in 1993. The record coolest high of 63 was set back in 1915. The official thermometer was located near Lake Michigan at the time. 23 of the last 32 lows (72%) were in the 60s. Six lows (19%) were in the cool 50s. Our most recent 50s low was 58 in 2004. Three lows (9%) were in the warm 70s. Our most recent 70s low was 71 in 1998. There was a string of 11 straight years of 60s lows from 1981 through 1991. Our current string of 60s lows is six years and counting, from 2005 to 2010.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:19 and sunrise is at 5:50. Sunset is at 20:08 and twilight ends at 20:39. There's a total of 14 hours, 18 minutes of daylight today and 15 hours, 20 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:20 and sunrise is at 5:51. The moon is waxing crescent and will reach first quarter tomorrow at 6:08. Illumination was 36% at midnight, will be 42% at noon and 48% at midnight tonight. Moonrise is at 13:00 this afternoon. Moonset is at 23:11 tonight. Moonrise is at 14:12 tomorrow afternoon. Moonlight time is 10 hours, 11 minutes which is 36 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 31 days.