August 8: ORD

Today is August 8th. It's the 221st day of the year. 145 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. Before this, the official site of record was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 83 and the normal low is 64. I've calculated the 33-year averages at 84 and 65.

On the hot side, in 1983 (O'Hare's warmest August 8th) the high was 98  with a low of 72. Five years later, in 1988, the high was 99 (O'Hare's hottest high of the date) with a low of 70. In 2001 the high was 93 with the record warmest low of 76. The record warmest low of 76 was originally set way back in 1896. 1988 and 2001 are O'Hare's co-second warmest August 8ths. The record high of 100 was set in 1934 at the University of Chicago. 20 of  the past 33 highs (61%) were in the 80s. O'Hare recorded seven consecutive 80s highs from 1992 through 1998. Five highs (15%) were in the hot 90s. Our most recent 90s high was 93 degrees in 2005. Eight highs (24%) were in the cool 70s. 

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 79 with a cold low of 49, a 30 degree spread. That low of 49 was O'Hare's lowest for the date and colder than the official record low which was set at Midway this same year. In 1970 the high was 76 with a low of 71, a five degree spread. In 1964 the low was a cool 51 degrees, also colder than the record low.

More recently, there were large spreads of 30 degrees in: 1985 (85/55), 1990 (85/55) and in 2005 (93/63). The lone small spread was seven degrees in 1987 (77/70).
 
On the cool side, in 1989 (O'Hare's second coolest August 8th) the high was 77 with a low of 53. A decade later, in 1999 (O'Hare's third coolest August 8th), the high was 72 with a low of 59. The other cool high was 72 in 1991. Those highs of 72 are O'Hare's coolest of the date. The record low of 52 was set in 1976 at Midway. The record coolest high of 62 was set way back in 1884, at a time when the official readings were taken adjacent to Lake Michigan. 16 of the last 33 lows (49%) were in the 60s. Ten lows (30%) were in the warm 70s. Seven lows (21%) were in the cold 50s, most recently 58 degrees in 2002. There's a three-way tie for O'Hare's coolest August 8th: 1964 (high of 77, low of 51 (a low colder than the record low)), 1972 (high of 74, low of 54) and 1976 (high of 79, low of 49 (O'Hare's coldest low of the date and a low colder than the record low)). 

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 waning gibbous, heading towards last quarter in tomorrow at 13:55. Illumination was 65% at midnight, will be 60% at noon and 55% at midnight tonight. Moonset is at 12:48 this afternoon. Moonrise is at 23:07 tonight. Moonset is at 13:47 tomorrow afternoon. Moonlight time is 13 hours, 41 minutes which is 28 minutes longer than yesterday. 

Summer began on June 4th and runs for 110 days through September 21st. High temperatures in this period are usually in the 70s and 80s. Highs in the 90s and 100s occur infrequently. Labor Day is in 26 days.