July 19: ORD

Today is July 19th. It's the 200th day of the year. 165 days remain. It's week 29 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 64. I've calculated the 32-year averages at 85 and 65.

On the hot side, in 1991 the high was 99 with a low of 72. Five years earlier, in 1986, the high was 95 with a low of 74. A year later, 1987, the high was 93 with a low of 75. Another really hot high was 96 in 1983. The record high of 101 was set back in 1930. Our warmest low was 76 in 1981. The record warmest low of 78 occurred in 1977. 21 of the past 32 highs (66%) were in the 80s. Six highs (19%) were in the hot 90s. Five highs (15%) were in the cool: 60s (1) and 70s (4). From 1979-2010, this is the average sixth hottest day of the year.

Yesterday's low at O'Hare was 80 degrees. This is a new record for the warmest low temperature for July 18th, breaking 78 in 1942. It was also our hottest July 18th (of the past 33 years). Overall the day was two degrees warmer than the prior hottest day of 1986 (high of 93, low of 75). The high yesterday was 92 at 17:23 with that record-breaking low of 80 at 6:04. The hottest temperature for the past 33 years for July 18th remains 96 degrees in 1991. Rockford had a high of 93 at 17:06 with a low of 79 at 6:56. That low of 79 tied the record warmest low for July 18th at Rockford, also set in 1942.

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 97 with a low of 77, a hot day. 1977 was also the year of the record warmest low of 78. In 1969 the high was 76 with a low of 69, a seven degree spread. In 1962 the high was 83 with a low of 53, a 30 degree spread.

More recently, there were large spreads of 30 degrees in 1984 (84/54) and 30 degrees in 2003 (83/53). The small spread was six degrees in 1989 (71/65).

On the cool side, in 2000 the high was 69 (our only 60s high) with a low of 56. Two years ago, in 2009, the high was 71 with a low of 57. There were four other 50s lows (53 in 2003, 54 in 1984, 55 in 1979 and 58 in 1992). The record low of 50 was set way back in 1873. There were three other highs in the 70s (71 in 1989, 78 in 1985 and 78 three years ago in 2008). The record coolest high of 65 occurred back in 1912. 20 of the last 32 lows (62%) were in the 60s. Six lows (19%) were in the cool 50s. Six lows (19%) were in the warm 70s. Our most recent 70s low was 70 in 1998.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:00 and sunrise is at 5:34. Sunset is at 20:25 and twilight ends at 20:58. There's a total of 14 hours, 51 minutes of daylight today and 15 hours, 58 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:01 and sunrise is at 5:34. The moon is waning gibbous. Illumination was 84% at midnight, will be 81% at noon and 77% at midnight tonight. Moonset is at 10:09 this morning. Moonrise is at 22:24 tonight. Moonset is at 11:09 tomorrow morning. Moonlight time is 11 hours, 45 minutes which is 37 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 five days.