July 3: ORD

Today is July 3rd. It's the 184th day of the year. 181 days remain. It's week 27 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 61. I've calculated the 32-year averages at 83 and 62.

On the hot side, in 1999 the high was 92 with a low of 76. In 2002 the high was 94 with a low of 73. There were three more 90s highs: 93 in 2003, 91 in 1991 and 91 in 1993. The record high of 102 was set in 1949. The record warmest low of 78 occurred back in 1911. 27 of the past 32 highs (84%) were in the: 70s (10) and 80s (17). Five highs were in the hot 90s. One temperature quirk was that back in 1935, this was the date of the first high of 85 degrees or more for that year! Official readings were taken at the University of Chicago at the time.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1974 the high was 94 with a warm low of 74, a hot day. In 1971 the high was 87 with a low of 57, a 30 degree spread. In 1968 the low was a cold 48 degrees, cooler than the record low. In 1967 the high was a cool 71 degrees. In 1963 the high was 67 with a low of 48, a cool day. That low of 48, just as with 1968, was cooler than the record low.

More recently, there were large spreads of: 34 degrees in 1988 (86/52), 32 degrees in 2005 (86/54), 30 degrees in 1979 (85/55), 30 degrees in 1980 (80/50) and 30 degrees in 1985 (83/53).

On the cool side, three years ago, in 2008, the high was 71 (our coolest high) with a low of 55. In 1996 the high was 76 with a low of 53. A decade earlier, in 1986, the high was 77 with a low of 52. The record low of 50 was set in 1980. There were two other cool lows: 52 in 1988 and 53 in 1985. The record coolest high of 63 occurred way back in 1909. 29 of the last 32 lows (91%) were in the: 50s (11) and 60s (18). Three lows were in the warm 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:47 and sunrise is at 5:22. Sunset is at 20:33 and twilight ends at 21:08. There's a total of 15 hours, 11 minutes of daylight today and 16 hours, 21 minutes between twilights. We lost a minute of daylight from yesterday. Tomorrow twilight begins at 4:48 and sunrise is at 5:22. The moon reached new two mornings ago at 3:54 and is waxing crescent. Illumination was 4% at midnight, will be 7% at noon and 10% at midnight tonight. Moonrise is at 7:56 this morning. Moonset is at 22:01 tonight. Moonrise is at 9:08 tomorrow morning. Moonlight time is 14 hours, 5 minutes which is 38 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. Independence Day is tomorrow.