July 5: ORD

Today is July 5th. It's the 187th day of the year. 179 days remain. It's week 27 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 63. I've calculated the 33-year averages at 84 and 63.

On the hot side, in 1999 (O'Hare's warmest July 5th) the high was 94 with a low of 79 (O'Hare's warmest low of the date). Five years prior, in 1994 (O'Hare's second warmest July 5th), the high was 95 with a low of 77 (tied with 1977 as O'Hare's third warmest low). O'Hare's hottest high was 98 in 1988. O'Hare's second warmest low was 78 two years ago, in 2010.  The record high of 102 and record warmest low of 82 were set on the same  hot day back in 1911, at a time when the official readings were taken adjacent to Lake Michigan. 32 of the past 33 highs (97%) were in the: 70s (9), 80s (15) and 90s (8). One high was in the cool 60s (67 in 1983). O'Hare's third warmest July 5th was in 1977 as the high was 94 with a low of 77 (tied with 1994 as O'Hare's third warmest low). 

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 94 with a warm low of 77, a hot day. In 1972 the high was 73 with a cold low of 44 (a low colder than the record low which was set this day at 46 degrees), a cool day. In 1967 the high was 66 (year of the record coolest high of 65) with a low of 48, a cool day. In 1965 the high was 79 with a cold low of 42 (a low colder than the record low), a 37 degree spread and overall cool day. In 1964 the high was 83 with a cold low of 46 (tied with the record low), a 37 degree spread. In 1963 the high was 85 with a cold low of 50, a 35 degree spread. In 1961 the high was a cool 69 with a low of 53, a cool day.

More recently, there were large spreads of: 38 degrees in 1988 (98/60), 36 degrees in 1980 (94/58), 35 degrees in 1982 (95/60) and 32 degrees in 1996 (86/54).

On the cool side, in 1983 (O'Hare' second coolest July 5th) the high was 67 with a low of 48. Four years earlier, in 1979, the high was 71 with a low of 47. The record low of 46 was set in 1972 at Midway. The record coolest high of 65 occurred in 1967 at Midway. 26 of the last 33 lows (79%) were in the: 50s (10) and 60s (16). O'Hare recorded consecutive lows in the 50s & 60s as follows: seven from 1987 through 1993 and seven from 2000 through 2006 (six of these were 60s). Five lows (15%) were in the warm 70s. Two lows (6%) were in the cold 40s (in 1979 and 1983). O'Hare's coolest July 5th was in 1967 as the high was 66 (O'Hare's coolest high of the date) with a low of 48. 1983 (see above) was the second coolest July 5th. The third coolest was in 1972 as the high was 73 with a low of 44 (O'Hare' second coldest low and colder than the record low). O'Hare's coldest low of 42 occurred in 1965 (a low colder than the record low). O'Hare had a low which ties the record (46 in 1964). 

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:49 and sunrise is at 5:23. Sunset is at 20:32 and twilight ends at 21:07. There's a total of 15 hours, 9 minutes of daylight today and 16 hours, 18 minutes between twilights. We lost a minute of daylight from yesterday. Tomorrow twilight begins at 4:50 and sunrise is at 5:24. The moon is waning gibbous, having reached the full Buck moon two days ago at 13:52. Illumination was 97% at midnight, will be 95% at noon and 92% at midnight tonight. Moonset was at 7:38 this morning. Moonrise is at 21:44 tonight. Moonset is at 8:48 tomorrow morning. Moonlight time is 9 hours, 54 minutes which is 35 minutes longer 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. Parent's Day is in 17 days.