June 5: ORD

Today is June 5th. It's the 157th day of the year. 209 days remain. It's week 23 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 76 and the normal low is 55. I've calculated the 33-year averages at 76 and 52.

On the hot side, in 2005 the high was 87 with a low of 68 (a co-warmest low of O'Hare for the date). In 1984 the high was 88 with a low of 66. The other hot highs were 89 in 1988 and 1999. The record high of 97 occurred in 1971 at Midway. The record warmest low of 77 occurred back in 1925, at a time when the official readings were taken adjacent to Lake Michigan. 25 of the past 33 highs (76%) were in the: 70s (13) and 80s (12). O'Hare recorded seven consecutive highs in the 70s & 80s from 1991 through 1997. Eight highs (24%) were in the cool: 50s (2) and 60s (6). O'Hare's warmest June 5th was in 1971 as the high was 92 (O'Hare's warmest high and only 90s high of the date) and low of 68 (a co-warmest low of O'Hare for the date). O'Hare's other co-warmest low of the date of 68 occurred in 1966. 
 
In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1974 the high was 73 with a low of 66, a small seven degree spread. In 1971 the high was 92 with a low of 68, a hot day and year of the record high. The same high and low in 1971 happened on both the 5th and 6th, a very rare occurrence. In 1966 the low was a warm 68 degrees. In 1961 the high was 86 with a low of 50, a 36 degree spread.

More recently, there were large spreads of 35 degrees in 1994 (87/52), 35 degrees two years ago (in 2009) (79/44), 34 degrees in 1987 (87/53), 33 degrees in 2004 (77/44), 33 degrees in 2006 (81/48), 32 degrees in 1988 (89/57), 31 degrees in 1981 (86/55) and 31 degrees in 2003 (78/47).

On the cool side, in 1998 (O'Hare's coolest June 5th) the high was 58 with a low of 42. In 2001 the high was 58 with a low of 47. In 1990 the high was 63 with a low of 42. The lows of 42 are O'Hare's coldest lows of the date. The highs of 58 are O'Hare's coolest highs of the date. The other cool highs were 61 in 1986, 63 in 2000 and 64 in 2007. The record low of 37 was set in 1945 at Midway. The record coolest high of 45 occurred way back in 1894, at a time when the official readings were taken adjacent to Lake Michigan. 27 of the last 33 lows (82%) were in the: 40s (15) and 50s (12). Six lows were in the warm 60s. All 12 lows in the 50s (over the past 33 years) happened between 1979 and 1995, most recently 55 in 1995. All lows from 1996 onward have been in the 40s or 60s. 5 of the 6 lows in the 60s happened from 1999 through 2011. The lone exception was a low of 66 in 1984, O'Hare's warmest day until 2005.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:44 and sunrise is at 5:18. Sunset is at 20:26 and twilight ends at 21:01. There's a total of 15 hours, 8 minutes of daylight today and 16 hours, 17 minutes between twilights. We didn't gain or lose any minutes of daylight from yesterday. Tomorrow twilight begins at 4:43 and sunrise is at 5:17. The moon is waning gibbous, having passed the full Strawberry (a.k.a. Rose or Hot) moon yesterday morning at 6:12. Illumination was 99% at midnight, will be 98% at noon and 95% at midnight tonight. Moonset was at 6:30 this morning. Moonrise is at 21:50 tonight. Moonset is at 7:40 tomorrow morning. Moonlight time is 8 hours, 40 minutes which is ten minutes longer than yesterday. 

Summer began yesterday, 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. Flag Day is in nine days.