July 18: ORD

Today is July 18th. It's the 199th day of the year. 166 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 66.

On the hot side, in 1986 the high was 93 and low of 75. Five years later, in 1991, the high was 96 with a low of 70. In 2005 the high was 91 with a low of 75. That high of 96 in 1991 was the hottest O'Hare has seen, however the record high of 100 was set in 1946. The record warmest low of 78 occurred in 1942. Other warm lows were 74 in both 1982 and 2008. 24 of the past 32 highs (75%) were in the: 80s (14) and 90s (10). Eight highs were in the cool 70s. From 1979-2010, this is the average fourth 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 1966 the high was 95 with a low of 67. The day falls short of being exceptionally hot. However, we do not hit 95 degrees all that often.

More recently, there were no small spreads of up to 7 degrees or large spreads of at least 30 degrees.

On the cool side, in 1979 the high was 82 with our coolest low of 45 degrees, a low colder than the record low. Three decades later, in 2009, the high was 72 with a low of 57. The record low of 53 was set in 1979 at Midway. Another cool high was 71 in 2000. The record coolest high of 62 occurred back in 1924. 26 of the last 32 lows (81%) were in the: 60s (16) and 70s (10). Lows were in the 60s or 70s for ten straight years from 1993 through 2002. Six lows were in the cool: 40s (1) and 50s (5).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:59 and sunrise is at 5:33. Sunset is at 20:26 and twilight ends at 20:59. There's a total of 14 hours, 53 minutes of daylight today and 16 hours between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:00 and sunrise is at 5:34. The moon is waning gibbous. Illumination was 91% at midnight, will be 88% at noon and 84% at midnight tonight. Moonset is at 9:08 this morning. Moonrise is at 22:00 tonight. Moonset is at 10:09 tomorrow morning. Moonlight time is 11 hours, 8 minutes which is 38 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 six days.