June 19: ORD

Today is June 19th. It's the 171st day of the year. 195 days remain. It's week 25 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 81 and the normal low is 59. I've calculated the 33-year averages at 80 and 59.

On the hot side, in 1995 (O'Hare's hottest June 19th) the high was 94 (O'Hare's hottest high of the date) with the first of two 70s lows of 71. In 1988 (O'Hare's second hottest June 19th) the high was 93 with the second 70s low of 71. Those lows of 71 are O'Hare's warmest of the date. The record high of 102 was set in 1953 at Midway. The record warmest low of 75 occurred back in 1931 at the University of Chicago. 18 of the past 33 highs (55%) were in the 80s. O'Hare recorded six consecutive 80s highs from 2006 through 2011. Three highs (9%) were in the hot 90s and 12 (36%) were in the cool: 60s (4) and 70s (8).
 
In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1970 the high was a cool 69 degrees. In 1965 the high was 82 with a low of 48, a 34 degree spread. In 1962 the high was a cool 67 degrees. In 1961 the high was 84 with a low of 52, a 32 degree spread. In 1959 the high was 82 with a low of 50, a 32 degree spread.

More recently, both spreads were large: 31 degrees in 1997 (85/54) and 30 degrees in 1991 (87/57).

On the cool side, in 2004 the high was 64 (O'Hare's coolest high of the date) with a low of 48. In 1980 the high was 69 with the record low of 43. 1980 and 2004 stand as O'Hare's co-coolest June 19th days. Another cold low was 47 in 1985. The other cool highs were 67 in 1992 and 68 in 2003. The record coolest high of 56 occurred back in 1926 at the University of Chicago. 28 of the last 33 lows (85%) were in the: 50s (14) and 60s (14). Three lows were in the cool 40s and two were in the warm 70s. Prior to 1979, O'Hare's coolest highs were 67 in 1962 and 69 in 1970.

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 5:17. Sunset is at 20:33 and twilight ends at 21:08. There's a total of 15 hours, 16 minutes of daylight today and 16 hours, 26 minutes between twilights. We gained no minutes of daylight from yesterday. Tomorrow twilight begins at 4:42 and sunrise is at 5:17. The moon reaches new today at 10:02. Illumination was 0% at midnight, will be 0% at noon and 0% at midnight tonight. Moonrise was at 5:22 this morning. Moonset is at 20:36 tonight. Moonrise is at 6:18 tomorrow morning. Moonlight time is 15 hours, 14 minutes which is four minutes shorter than yesterday. Moonlight time is at its peak today. Too bad it's not visible!

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 15 days.