July 11: ORD

Today is July 11th. It's the 192nd day of the year. 173 days remain. It's week 28 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 63. I've calculated the 32-year averages at 83 and 62.

On the hot side, in 1980 the high was 95 with a low of 72. In 1987 the high was 91 with a low of 69. The other 90s highs were 93 in 1983, 90 in 1979 and 90 in 1988 (our most recent 90s high). The record high of 97 and record warmest low of 80 were set on the same hot day back in 1936. 27 of the past 32 highs (84%) were in the: 70s (10) and 80s (17). Five highs were in the hot 90s.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1975 today (the 11th) and tomorrow (the 12th) the temperatures were the same: a high of 76 with a low of 56. In 1972 the low was a warm 75 degrees (O'Hare's warmest low for July 11). In 1968 the high was 80 with a cool low of 50, a 30 degree spread. In 1965 the low was a cool 51 degrees. In 1963 the high was 88 with a low of 53, a 35 degree spread. In 1961 the high was 86 with a low of 55, a 31 degree spread.

More recently, there were large spreads of 30 degrees in 1994 (84/54) and 30 degrees in 1997 (84/54).

On the cool side, in 1996 the high was 82 with the record low of 50, a 32 degree spread. The former record low was 51 in 1978 at Midway. In 1999 the high was 81 with a low of 52 (our most recent 50s low). The record coolest high of 65 occurred way back in 1873. 25 of the last 32 lows (78%) were in the 60s. There have been two amazing streaks of 60 degree lows: an eight year streak from 1986 to 1993 and then a current 11 year streak from 2000 to 2010. Six lows were in the cool 50s. One low was in the warm 70s (72 in 1980).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:53 and sunrise is at 5:27. Sunset is at 20:30 and twilight ends at 21:04. There's a total of 15 hours, 3 minutes of daylight today and 16 hours, 11 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 4:54 and sunrise is at 5:28. The moon is waxing gibbous. Illumination was 82% at midnight, will be 86% at noon and 89% at midnight tonight. Moonset is at 1:53 this morning. Moonrise is at 17:28 this afternoon. Moonset is at 2:45 tomorrow morning. Moonlight time is 8 hours, 25 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. Parent's Day is in 13 days.