July 16: ORD

Today is July 16th. It's the 198th day of the year. 168 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. 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 84 and the normal low is 64. I've calculated the 33-year averages at 86 and 65.

On the hot side, in 1988 (O'Hare's warmest July 16th) the high was 99 with a low of 70. In 2006 the high was 94 with a low of 74. In 1995 the high was 93 with a low of 74. Those lows of 74 were O'Hare's second warmest lows of the date. O'Hare's warmest low of the date was 75 in 1982. The record high of 100 was set way back in 1887. The record warmest low of 80 occurred way back in 1878. Both records were set at a time when the official readings were taken adjacent to Lake Michigan. 30 of the past 33 highs (91%) were in the: 80s (17) and 90s (13). For 19 consecutive years, from 1993 through last year, 2011, highs were in the 80s and 90s. Three highs were in the cool 70s, most recently 75 in 1992. Through 2011, this is the average third 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 1967 the high was 79 with a cold low of 49, a 30 degree spread. That low of 49 equals the record low of 49. In 1962 the high was a cool 72 degrees.

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

On the cool side, in 1979 (O'Hare's second coolest July 16th) the high was 74 with a low of 55. In 1987 the high was 80 with a low of 52, O'Hare's second coldest low of the date. The record low of 49 was set in 1945 at Midway. The record coolest high of 62 occurred back in 1912, at a time when the official readings were taken adjacent to Lake Michigan. 27 of the last 33 lows (82%) were in the: 60s (16) and 70s (11). Six lows were in the cool 50s, most recently 59 in 2003. O'Hare's coolest July 16th was in 1967 as the high was 79 with a low of 49, O'Hare's coldest low of the date and is equal to the official record low. O'Hare's coolest high of 72 occurred in 1962.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:58 and sunrise is at 5:32. Sunset is at 20:27 and twilight ends at 21:00. There's a total of 14 hours, 55 minutes of daylight today and 16 hours, 2 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 4:59 and sunrise is at 5:32. The moon is waning crescent. Illumination was 8% at midnight, will be 6% at noon and 4% at midnight tonight. Moonrise was at 3:16 this morning. Moonset is at 18:32 tonight. Moonrise is at 4:10 tomorrow morning. Moonlight time is 15 hours, 16 minutes which is 1 minute shorter than yesterday. Moonlight is at its peak today.

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. Parent's Day is in six days.