August 9: ORD

Today is August 9th. It's the 221st day of the year. 144 days remain. It's week 32 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 84 and 64.

On the hot side, two years ago (in 2009) the high was 91 with a low of 77. In 2001 the high was 95 with a low of 72. Another high of 95 occurred in 2005. There were two highs of 93 (1984 and 1992). The record high of 97 and record warmest low of 79 were set on the same hot day back in 1913. Other warm lows were 77 in 1934 and 73 in 1988. 16 of the past 32 highs (50%) were in the 80s. Eight highs (25%) were in the hot 90s. Eight highs (25%) were in the cool: 60s (1) and 70s (7). Our most recent 70s high was 77 in 2003.

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1976 the high was 83 with a cool low of 51, a 32 degree spread. That low of 51 equals the record low. In 1972 the low was a cool 51 degrees, equal to the record low of 51 set at Midway. In 1966 the low was a cool 52 degrees. In 1964 the high was 70 with a low of 45, a cool day. That low of 45 was also colder than the record low. The high on the 7th in 1964 was 92. That's a big 47-degree drop to the 45 degree low (in 1964).

More recently, there were large spreads of 34 degrees in 1985 (90/56) and 30 degrees in 2005 (95/65). The small spread was seven degrees in 1983 (79/72).

On the cool side, in 1994 the high was a cool 66 (our only 60s high) with a low of 53. In 1982 the high was 74 with a low of 56. In 1999 the high was 77 with a low of 54. The other mid 50s lows were 55 in 1990 and 56 in 1985. The record low of 51 was set in 1972 at Midway. The record coolest high of 64 was set way back in 1884. The official thermometer was located near Lake Michigan at the time. 16 of the last 32 lows (50%) were in the 60s. Nine lows (28%) were in the cool 50s. Our most recent 50s low was 57 in 2002. Seven lows (22%) were in the warm 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:23 and sunrise is at 5:54. Sunset is at 20:03 and twilight ends at 20:34. There's a total of 14 hours, 9 minutes of daylight today and 15 hours, 11 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:24 and sunrise is at 5:55. The moon is waxing gibbous, having reached first quarter three days ago at 6:08. Illumination was 79% at midnight, will be 83% at noon and 87% at midnight tonight. Moonset is at 1:37 this morning. Moonrise is at 17:15 this afternoon. Moonset is at 2:39 tomorrow morning. Moonlight time is 8 hours, 22 minutes which is 1 minute longer than yesterday. Moonlight time is at it's shortest 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. Labor Day is in 27 days.