June 11: ORD

Today is June 11th. It's the 163rd day of the year. 203 days remain. It's week 24 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 78 and the normal low is 57. I've calculated the 33-year averages at 78 and 56.

On the hot side, in 2005 (O'Hare's second warmest June 11th) the high was 88 with a low of 72 (O'Hare's warmest low of the date). In 1999 the high was 90 with a low of 66. The other hot high was 90 in 1983. The other warm low was 69 in 2002. The record high of 97 was last tied in 1954 at Midway after originally being set back in 1933 at the University of Chicago. The record warmest low of 77 occurred in 1973 at Midway. 24 of the past 33 highs (73%) were in the: 70s (9) and 80s (15). Our most recent 70s high was 76 in 1998. O'Hare recorded nine consecutive 70s & 80s highs from 1986 through 1994. Two highs (6%) were in the hot 90s. Seven highs (21%) were in the cool: 50s (1) and 60s (6). O'Hare's hottest June 11th was in 1973 as the high was 91 with a low of 71. O'Hare's hottest high was 93 degrees in 1976.

In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1976 the high was a hot 93 degrees. In 1973 the high was 91 with a low of 71, a hot day and year of the record warmest low. In 1972 the high was 74 with a cold low of 36, a 38 degree spread and overall cool day. That low of 36 was cooler than the record low. In 1970 the low was a warm 70 degrees. In 1966 the high was 78 with a cold low of 41, a 37 degree spread. In 1963 the high was a cool 65 degrees. In 1961 the high was a hot 90 with a low of 56, a 34 degree spread. In 1959 the low was a warm 69 degrees.

More recently, the spreads were all large: 40 degrees in 1988 (87/47), 34 degrees in 1982 (77/43), 34 degrees in 1994 (85/51), 33 degrees in 1980 (74/41), 32 degrees in 1983 (90/58), 32 degrees in 1989 (76/44), 32 degrees in 1992 (83/51) and 30 degrees in 1990 (80/50).

On the cool side, in 1985 (O'Hare's coolest June 11th) the only 50s high of 56 occurred with a low of 48. Last year, in 2011, the high was 62 with a low of 52. The other cool lows were the record low of 41 in 1980, 43 in 1982 and 44 in 1989. The record low of 41 was originally set at Midway International Airport in 1972. Three years ago, in 2009 and in 2006 the highs were a cool 64 degrees. The record coolest high of 48 was set way back in 1903, at a time when the official readings were taken adjacent to Lake Michigan. 27 of the last 33 lows (82%) were in the: 50s (17) and 60s (10). Five lows were in the cold 40s. All of the 40s lows over the last 33 years occurred from 1980 through 1989. One low (72 in 2005) was in the warm 70s. There have been only three 70s lows on this date in the history of O'Hare International Airport. O'Hare also had a cold low of 41 in 1966 which ties 1980 as O'Hare's coldest low. O'Hare's second coolest June 11th was in 1972 as the high was 74 with a cold low of 36 (a low colder than the record low).

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:42 and sunrise is at 5:16. Sunset is at 20:30 and twilight ends at 21:04. There's a total of 15 hours, 14 minutes of daylight today and 16 hours, 22 minutes between twilights. We  gained two minutes of daylight from yesterday. Tomorrow twilight begins at 4:42 and sunrise is at 5:16. The moon reaches last quarter today at 5:41. Illumination was 52% at midnight, will be 47% at noon and 42% at midnight tonight. Moonrise was at 0:43 this morning. Moonset is at 13:13 this afternoon. Moonrise is at 1:09 tomorrow morning. Moonlight time is 12 hours, 30 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. Flag Day is in three days. Father's Day is in six days.