August 2: ORD

Today is August 2nd. It's the 215th day of the year. 151 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. 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 85 and 64.

On the hot side, in 1988 (O'Hare's warmest August 2nd) the high was the former record high of 100 with the record warmest low of 79. In 2006 (O'Hare's second warmest August 2nd) the high was 97 with a low of 77. The other hot highs were the record high of 101 set in 1991 and a high of 96 in 1987. 17 of the past 33 highs (52%) were in the 80s. O'Hare recorded consecutive 80s highs as follows: seven from 1977 through 1983 and seven from 1998 through 2004. Nine highs (27%) were in the hot: 90s (7) and 100s (2). Seven highs (21%) were in the cool 70s. O'Hare's third warmest August 2nd was in 1964 as the high was 96 with a low of 76. 

In looking back through the years to the first August at O'Hare in 1959, the following instances were notable: In 1975 the high was 78 with a low of 73, a five degree spread. In 1966 the high was 71 with a low of 52, a cool day. In 1965 the high was 73 with a cold low of 49, a cool day. That low of 49 is colder than the record low. In 1964 the high was 96 with a low of 76, a hot day. In 1962 the high was 83 with a low of 53, a 30 degree spread.

More recently, there were no other large or small spreads.

On the cool side, in 1985 the high was 77 with the record low of 51. In 1994 the high was 77 with a low of 56. The record coolest high of 63 occurred back in 1927 at the University of Chicago. 17 of the last 33 lows (52%) were in the 60s. Nine lows (27%) were in the cool 50s. Seven lows (21%) were in the warm 70s. O'Hare's coolest August 2nd was in 1965 as the high was 73 (O'Hare's second coolest high of the date) with a low of 49 (a low colder than the official record low). O'Hare's second coolest August 2nd was in 1966 as the high was 71 (O'Hare's coolest high of the date) with a low of 52.

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 20:11 and twilight ends at 20:42. There's a total of 14 hours, 23 minutes of daylight today and 15 hours, 26 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:17 and sunrise is at 5:49. The moon is waning gibbous, having reached the full Sturgeon (a.k.a. Green Corn) moon last night at 22:27. Illumination was 100% at midnight, will be 99% at noon and 98% at midnight tonight. Moonset was at 6:27 this morning. Moonrise is at 20:14 tonight. Moonset is at 7:35 tomorrow morning. Moonlight time is 10 hours, 13 minutes which is 37 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 32 days.