July 24: ORD

Today is July 24th. It's the 205th day of the year. 160 days remain. It's week 30 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 84 and the normal low is 64. I've calculated the 32-year averages at 85 and 64.

On the hot side, in 2005 the high was 102 with the record warmest low of 78. The record warmest low of 78 was first set in 1940. In 1987 the high was 92 with a low of 75. Our second hottest high was 94 in 1999. The record high of 105 was set back in 1934, the hottest temperature ever recorded in Chicago's history. An interesting sidebar was that for ten straight years from 1989 to 1998, there were no highs of 90 or above. 20 of the past 32 highs (63%) were in the 80s. Eight highs (25%) were in the hot: 90s (7) and 100s (1). Our most recent 90s high was 90 in 2001. Four highs (12%) were in the cool 70s.

In looking back through the years to the first July at O'Hare in 1959, there were no notable instances of significantly hot or cool temperatures from 1959-1978.

More recently, there was a large temperature spread (diurnal) of 32 degrees in 1988 as the high was 91 with a low of 59.

On the cool side, in 2004 the high was 71 with a low of 55. Four years earlier, in 2000, the high was 79 with the record low of 53. The record coolest high of 66 was set way back in 1896. The other cool highs were 74 in 1992 and 79 in 2002. Another cool low was 54 in 2003. 18 of the last 32 lows (56%) were in the 60s. Eight lows (25%) were in the cool 50s. Six lows (19%) were in the warm 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:05 and sunrise is at 5:38. Sunset is at 20:21 and twilight ends at 20:54. There's a total of 14 hours, 43 minutes of daylight today and 15 hours, 49 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:07 and sunrise is at 5:39. The moon is waning crescent, having reached last quarter yesterday at 0:02. Illumination was 40% at midnight, will be 36% at noon and 31% at midnight tonight. Moonrise is at 0:10 this morning. Moonset is at 15:08 this afternoon. Moonrise is at 0:47 tomorrow. Moonlight time is 14 hours, 58 minutes which is 50 minutes longer 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 today.