July 15: ORD

Today is July 15th. It's the 196th day of the year. 169 days remain. It's week 28 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 84 and the normal low is 63. I've calculated the 32-year averages at 86 and 65.

On the hot side, in 1980 the high was 98 with the record warmest low of 82. In 1995 the high was 98 with a low of 75. In 1988 the high was the record high of 102 with a low of 70, a 32 degree spread. In 2006 the high was 97 with a low of 74. 27 of the past 32 highs (84%) were in the: 80s (17) and 90s (10). We've had 80s or 90s for the past 18 straight years (1993-2010). One high was in the hot 100s. Four highs were in the cool 70s. Our most recent 70s high was 77 in 1992. Through 2010, this is the average second hottest day of the year.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1977 the high was a hot 98 with a low of 74, a hot day. In 1967 the high was 70 with a low of 49, a cool day. That low of 49 was colder than the record low of 52, which occurred this year (1967). In 1964 the high was 88 with a low of 56, a 32 degree spread. In 1962 the high was a cool 67 with a low of 60, a seven degree spread.

More recently, there was a small spread of seven degrees in 1981 (75/68). There were large spreads of 33 degrees in 1991 (87/54) and 31 degrees in 2002 (91/60).

On the cool side, in 1987 the high was 70 with a low of 54. Three years later, in 1990, the high was 72 with a low of 61. Another cool low was 54 in 1991. The record low of 52 was last set in 1967 at Midway, having first been set in 1945. The record coolest high of 65 occurred back in 1903. 17 of the last 32 lows (53%) were in the 60s. Six lows (19%) were in the cool 50s. Our most recent 50s low was 59 in 2004. Nine lows (28%) were in the warm: 70s (8) and 80s (1).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:57 and sunrise is at 5:30. Sunset is at 20:28 and twilight ends at 21:01. There's a total of 14 hours, 58 minutes of daylight today and 16 hours, 4 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 4:58 and sunrise is at 5:31. The moon is full as the full Buck or Thunder moon today at 1:40. Illumination was 100% at midnight, will be 100% at noon and 99% at midnight tonight. Moonset is at 5:55 this morning. Moonrise is at 20:38 tonight. Moonset is at 7:01 tomorrow morning. Moonlight time is 9 hours, 17 minutes which is 31 minutes longer 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. Parent's Day is in nine days.