August 1: ORD

Today is August 1st. It's the 213th day of the year. 152 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 65.

On the hot side, in 2006 the high was 99 with the record warmest low (and only 80s low) of 80. In 1988 the high was the record high of 100 with the former record warmest low of 78. In 1987 the high was 97 with a low of 77. Other hot highs were 95 in 1991 and 94 in 2002. Other warm lows were 76 in 2001 and 75 in 2002 (our most recent 70s low). 17 of the past 32 highs (53%) were in the 80s. Nine highs (28%) were in the hot: 90s (8) and 100s (1). Six highs (19%) were in the cool 70s. An interesting side bar is that for nine years in a row, from 1992 to 2000, there were no highs in the 90s. From 1979-2010, this is the average fifth 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 1974 the high was a cool 67 with a low of 62, a five degree spread. In 1973 the high was a cool 70 degrees. In 1965 the high was a cool 69 with a low of 54, a cool day. In 1961 the high was 77 with a low of 71, a six degree spread.

More recently, there was a large spread of 32 degrees in 1991 (95/63).

On the cool side, in 1990 the high was 76 with the record low of 51. The former record low was 52 in 1947. In 1985 the high was 75 with a low of 54. In 1979 we had our coolest high (of the past 32 years) of 70 with a low of 60. The record coolest high of 66 occurred way back in 1875. The official thermometer was located near Lake Michigan at the time. 20 of the last 32 lows (62%) were in the 60s, including seven of the last eight lows (88%). Six lows (19%) were in the cool 50s. Our most recent 50s low was 57 in 1996. 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 5:14 and sunrise is at 5:46. Sunset is at 20:13 and twilight ends at 20:44. There's a total of 14 hours, 27 minutes of daylight today and 15 hours, 30 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:15 and sunrise is at 5:47. The moon is waxing crescent, having become new two days ago at 13:40. Illumination was 3% at midnight, will be 5% at noon and 8% at midnight tonight. Moonrise is at 8:05 this morning. Moonset is at 21:02 tonight. Moonrise is at 9:19 tomorrow morning. Moonlight time is 12 hours, 57 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 35 days.