July 26: ORD

Today is July 26th. It's the 208th day of the year. 158 days remain. It's week 30 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 83 and 65.

On the hot side, in 1997 (O'Hare's warmest July 26th) the high was 97 (O'Hare's most recent 90s high and hottest high of the date) with a low of 73. In 1982 the high was 91 with a low of 73. Those lows of 73 are O'Hare's warmest lows of the date. The record high of 99 was set in 1955 at Midway. The record warmest low of 80 occurred back in 1916, at a time when the official readings were taken adjacent to Lake Michigan. 23 of the past 33 highs (70%) were in the 80s. O'Hare recorded seven consecutive 80s highs from 2005 through 2011. Three highs (9%) were in the hot 90s. Seven highs (21%) were in the cool: 60s (1) and 70s (6). Our most recent 70s high was 74 in 2004. There have been two significant stretches of sub-90 degree highs. The first was nine years from 1988 through 1996 and the second is still ongoing, 14 years from 1998 through 2011. O'Hare's second hottest high of the date is 93 degrees in 1966.

In looking back through the years to the first July at O'Hare in 1959, the following instances were notable: In 1972 the high was a cool 70 with a low of 63, a seven degree spread. In 1962 the high was 75 with a cold low of 49, a cool day.

More recently, there was a small spread of five degrees in 1981 (71/66).

On the cool side, in 1984 (O'Hare's coolest July 26th) the high was 67 (O'Hare's only 60s high and coolest high of the date) with a low of 55. In 1991 the high was 78 with the record low of 53. The record low of 53 was originally set in 1962. The other cool high was 71 in 1981. The record coolest high of 66 occurred way back in 1891, at a time when the official readings were taken adjacent to Lake Michigan. 18 of the last 33 lows (55%) were in the 60s. Seven lows (21%) were in the cold 50s. Our most recent 50s low was 59 degrees in 2004. Eight lows (24%) were in the warm 70s. O'Hare's second coolest July 26th was in 1962 as the high was 75 with a low of 49 (O'Hare's coldest low of the date and a low colder than the official record low).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 5:08 and sunrise is at 5:41. Sunset is at 20:18 and twilight ends at 20:51. There's a total of 14 hours, 37 minutes of daylight today and 15 hours, 43 minutes between twilights. We lost two minutes of daylight from yesterday. Tomorrow twilight begins at 5:09 and sunrise is at 5:42. The moon reaches first quarter today at 3:56. Illumination was 49% at midnight, will be 54% at noon and 60% at midnight tonight. Moonrise is at 14:04 this afternoon. Moonset is at 0:14 tomorrow morning. Moonrise is at 15:15 tomorrow afternoon. Moonlight time is 9 hours, 56 minutes which is 45 minutes shorter than yesterday. 

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. Labor Day is in 39 days.