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 31-year averages at 86 and 64.

On the hot side, in 1988 the high was 96 with the record warmest low of 80. Other hot highs were 96 in 1983, 96 in 1987 and 95 in 1982. The record high of 98 was set in 1964 at Midway. 17 of the last 31 highs were 80s. Ten highs were in the warmer 90s. Four highs were in the cooler 70s. Through 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 cool low of 49, a 31 degree spread. In 1972 the high was a cool 71. In 1966 the high was 77 with a cool 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. 1964 the high was 96 with a low of 76, a hot day and year of the record high.

More recently, there was a large spread of 34 degrees in 1983 (96/62), 32 degrees in 1994 (88/56), 31 degrees in 1985 (81/50) and 31 degrees in 2002 (90/59). There was a small spread of seven degrees in 1995 (78/71).

On the cool side, there were no days of a mean of at least 11.5 degrees below normal. 2000 was the coolest day, as the high was 72 (the coolest high of the past 31 years) with a low of 54. The coolest low was 50 in 1985. The record low of 48 and record coolest high of 62 occurred on the same day way back in 1894. The official thermometer was located near Lake Michigan at the time. 17 of the last 31 lows were 60s. Eight lows were in the cooler 50s. Six were in the warmer: 70s (5) and 80s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:17 and sunrise is at 5:48. Sunset is at 20:10 and civil twilight ends at 20:41. Nautical twilight ends at 21:20 and astronomical twilight ends at 22:04. There's a total of 14 hours, 22 minutes of daylight today and 15 hours, 24 minutes between twilights. We are losing about two minutes of daylight a day. Tomorrow twilight begins at 5:18 and sunrise is at 5:49. The moon is waning crescent and reached last quarter last night at 23:59, a minute to midnight. Illumination was 50% at midnight, will be 45% at noon and 39% at midnight tonight. Moonset is at 14:25 this afternoon. Moonrise is at 23:56 tonight. Moonset is at 15:30 tomorrow afternoon. Moonlight time is 14 hours, 29 minutes which is 28 minutes longer than yesterday. -Bernie-