June 29: ORD

Today is June 29th. It's the 181st day of the year. 185 days remain. It's week 26 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 83 and the normal low is 62. I've calculated the 33-year averages at 81 and 61.

On the hot side, in 1991 (O'Hare's second warmest June 29th) the high was 96 with a low of 71. A decade before, in 1981, the high was 96 with a low of 70. Those highs of 96 were O'Hare's hottest for June 29th. O'Hare's warmest lows of the date were 73 degrees in 1971, 1996 and 2005. The record high of 97 was set in 1954 at Midway. The record warmest low of 80 occurred in 1931 at the University of Chicago. 28 of the past 33 highs (85%) were in the: 70s (14) and 80s (14). Four highs were in the hot 90s. One high was in the cool 60s. The lone 60s high was 68. It occurred on one of the two coolest days of the past 33 years in 1984. O'Hare's warmest June 29th was in 1971 as the high was 95 (O'Hare's second hottest high of the date) with a low of 73.

In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1971 the high was a hot 95 degrees. In 1966 the high was 89 with a low of 57, a 32 degree spread.

More recently, there was a large spread of 34 degrees in 1992 (88/54).

On the cool side, in 1989 (O'Hare's coolest June 29th) the high was 73 with the record low (and only 40s low) of 48. Five years before, in 1984, the high was 68 (O'Hare's coolest high of the date) with a low of 53. The other cool highs were 70 in: 1982, 1988 and 2007. The record coolest high of 59 was set way back in 1902, at a time when the official readings were taken adjacent to Lake Michigan. 28 of the last 33 lows (85%) were in the: 50s (14) and 60s (14). One low was in the cold 40s and four lows were in the warm 70s.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:45 and sunrise is at 5:20. Sunset is at 20:34 and twilight ends at 21:08. There's a total of 15 hours, 14 minutes of daylight today and 16 hours, 23 minutes between twilights. We lost no minutes of daylight from yesterday. Tomorrow twilight begins at 4:46 and sunrise is at 5:20. The moon is waxing gibbous, having reached first quarter three nights ago at 22:30. Illumination was 73% at midnight, will be 78% at noon and 83% at midnight tonight. Moonset was at 1:33 this morning. Moonrise is at 16:17 this afternoon. Moonset is at 2:16 tomorrow morning. Moonlight time is 9 hours, 16 minutes which is 36 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. Independence Day is in five days.