August 3: ORD

Today is August 3rd. It's the 215th day of the year. 150 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 86 and 64.

On the hot side, in 1988 the high was 96 with the record warmest low of 80. In 2005 the high was 93 with a low of 74. In 1987 the high was 96 with a low of 70. In 1982 the high was 95 with a low of 68. Another hot high was 96 in 1983. The record high of 98 was set in 1964 at Midway. The record high of 98 was originally set in 1930 and tied again in 1944. 18 of the past 32 highs (56%) were in the 80s. Ten highs (31%) were in the hot 90s. Four highs (13%) were in the cool 70s. From 1979-2010, this is the average ninth hottest day of the year.

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 80 with a cold low of 49, a 31 degree spread. In 1972 the high was a cool 71 degrees. In 1966 the high was 77 with a cold low of 48, a cool day. That low of 48 equals the record low. In 1965 the high was 75 with a cool low of 50, a cool day. In 1964 the high was 96 with a low of 76, a hot day and year of the record high of 98 at Midway.

More recently, there was a large spread of 34 degrees in 1983 (96/62), 32 degrees in 1994 (88/56) and 31 degrees in 2002 (90/59). There was a small spread of seven degrees in 1995 (78/71).

On the cool side, in 2000 the high was 72 (the coolest high of the past 31 years) with a low of 54. In 1985 the high was 81 with a low of 50. In 1992 the high was 76 with a low of 56. The other 70s highs were 78 in 1995 and 79 in 2003. The record low of 48 and record coolest high of 62 occurred on the same cool day way back in 1894. The official thermometer was located near Lake Michigan at the time. 18 of the last 32 lows (56%) were in the 60s. Eight lows (25%) were in the cool 50s, most recently 59 in 2002. Six lows (19%) were in the warm: 70s (5) and 80s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:16 and sunrise is at 5:48. Sunset is at 20:10 and twilight ends at 20:42. There's a total of 14 hours, 22 minutes of daylight today and 15 hours, 26 minutes between twilights. We lost three minutes of daylight from yesterday. Tomorrow twilight begins at 5:18 and sunrise is at 5:49. The moon is waxing crescent and will reach first quarter in three days at 6:08. Illumination was 16% at midnight, will be 21% at noon and 26% at midnight tonight. Moonrise is at 10:33 this morning. Moonset is at 22:02 tonight. Moonrise is at 11:47 tomorrow morning. Moonlight time is 11 hours, 29 minutes which is 44 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 33 days.