June 16: ORD

Today is June 16th. It's the 168th day of the year. 198 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 80 and the normal low is 58. I've calculated the 33-year averages at 80 and 58.

On the hot side, in 1994 (O'Hare's hottest June 16th) the high was 95 (O'Hare's hottest high of the date) with a low of 74 (O'Hare's warmest low of the date). In 2006 the high was 90 with a low of 72. The other hot high was 93 in 2007. The record high of 98 was set way back in 1913, at a time when the official readings were taken adjacent to Lake Michigan. The record warmest low of 76 occurred in 1952 at Midway. 26 of the past 33 highs (79%) were in the: 70s (11) and 80s (15). O'Hare recorded consecutive 70s & 80s highs as follows: six from 1988 through 1993 and six from 2000 through 2005. Four highs were in the hot 90s and three were in the cool 60s. O'Hare's pre-1979 hot high was 92 in 1977.

In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1977 the high was a hot 92 with a low of 62, a 30 degree spread. In 1974 the high was a cool 61 with a low of 53, a cool day. In 1972 the high was a cool 60 with a low of 49, a cool day. In 1971 the high was 86 with a low of 56, a 30 degree spread. In 1965 the high was a cool 66 with a low of 49, a cool day. In 1964 the high was 65 with a low of 45, a cool day. In 1961 the high was 79 with a cold low of 41, a 38 degree spread.

More recently, the spreads were all large: 33 degrees in 1986 (86/53), 32 degrees in 1996 (88/56) and 31 degrees in 2001 (86/55).

On the cool side, in 1982 (O'Hare's coolest June 16th) the high was 62 with a low of 45. Two years earlier, in 1980, the high was 64 with the record low of 44. That record low of 44 was originally set in 1947 at Midway. The other cool high is 68 in 1999. The record coolest high of 54 occurred way back in 1879, at a time when the official readings were taken adjacent to Lake Michigan. 29 of the last 33 lows (88%) were in the: 50s (18) and 60s (11). Two lows were in the cold 40s and two were in the warm 70s. Prior to 1979, O'Hare had a low of 41 in 1961, its coldest low of the date and colder than the record low. The pre-1979 cool highs were 60 in 1972 (O'Hare's coolest high of the date) and 61 in 1974.

In regards to last year, 2011: the 45 degree drop in temperature from the high of 95 on 6/8/11 to the low of 50 late 6/9/11 was the greatest two-day drop in temperature since the June record drop of 49 degrees in 1988, 24 years ago. The drop in 1988 was from a high of 103 on June 25 to a low of 54 on June 26. The all-time record, irregardless of month, was a 61 degree drop from 74 degrees to 13 degrees on November 11 and 12, 1911. Data courtesy of The Chicago Weather Center Blog.

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 20:32 and twilight ends at 21:07. There's a total of 15 hours, 16 minutes of daylight today and 16 hours, 25 minutes between twilights. We gained no minutes of daylight from yesterday. Tomorrow twilight begins at 4:42 and sunrise is at 5:16. The moon is waning crescent. Illumination was 10% at midnight, will be 7% at noon and 5% at midnight tonight. Moonrise was at 3:08 this morning. Moonset is at 18:06 tonight. Moonrise is at 3:47 tomorrow morning. Moonlight time is 14 hours, 58 minutes which is 22 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. Father's Day is tomorrow.