June 12: ORD

Today is June 12th. It's the 164th day of the year. 202 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 79 and the normal low is 57. I've calculated the 33-year averages at 78 and 58.

On the hot side, in 2008 (O'Hare's hottest June 12th) the high was 91 with a low of 73 (O'Hare's warmest low of the date). In 1987 (tied with 1976 as O'Hare's third hottest June 12th) the high was 93 with a low of 67. All of the 90s highs (except in 2008) occurred between 1983 and 1988. The hot highs were 93 in 1983 and 91 in 1984. The two highs of 93 (in 1983 and 1987) are O'Hare's second hottest of the date. The other warm low was 70 in 2005. The record high of 97 was set in 1956 at Midway. The record warmest low of 75 occurred back in 1920, at a time when the official readings were taken adjacent to Lake Michigan. 22 of the past 33 highs (67%) were in the: 70s (10) and 80s (12). O'Hare recorded 11 consecutive 70s & 80s highs from 1989 through 1999. Of these 11, seven (64%) were in the 80s. Five highs (15%) were in the hot 90s. Six highs (18%) were in the cool: 50s (1) and 60s (5). O'Hare's second hottest June 12th was in 1967 as the high was 90 with a low of 72 (the second warmest low of the date). In 1976 (tied with 1987 as the third hottest June 12th) the high was 94 (O'Hare's hottest high of the date) with a low of 66.

In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1978 the high was 78 with a low of 48, a 30 degree spread. In 1977 the high was a cool 63 with a low of 57, a six degree spread. In 1976 the high was a hot 94 with a low of 66, a hot day. In 1967 the high was 90 with a warm low of 72, a hot day. In 1965 the high was 80 with a low of 50, a 30 degree spread. In 1960 the high was a cool 59 with a low of 55, a four degree spread.

More recently, the spreads were all large: 36 degrees in 1988 (90/54), 35 degrees in 1984 (91/56), 35 degrees in 1992 (86/51) and 33 degrees in 1983 (93/60).

On the cool side, in 1985 (O'Hare's coolest June 12th) the high was 57 (O'Hare's coolest high of the date) with the record low of 40. O'Hare's only other 50s high was 59 in 1960. In 2000 the high was 60 with a low of 53, a seven degree spread. The other cool high of 67 occurred in 2003. The record coolest high of 55 occurred in 1955 at Midway. 28 of the last 33 lows (85%) were in the: 50s (14) and 60s (14). Three lows were in the cool 40s (most recently 49 three years ago in 2009) and two were in the warm 70s (most recently 73 four years ago in 2008). Last year, 2011, wound up being an exceptionally cool day. The high of 64 and low of 50 (mean of 57) put it just half a degree outside of being one of the coolest June 12th days since 1979.

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 20:30 and twilight ends at 21:05. There's a total of 15 hours, 14 minutes of daylight today and 16 hours, 23 minutes between twilights. We didn't gain any minutes of daylight from yesterday. Tomorrow twilight begins at 4:42 and sunrise is at 5:16. The moon is waning crescent, having reached last quarter yesterday at 5:41. Illumination was 42% at midnight, will be 37% at noon and 33% at midnight tonight. Moonrise was at 1:09 this morning. Moonset is at 14:13 this afternoon. Moonrise is at 1:35 tomorrow morning. Moonlight time is 13 hours, 4 minutes which is 34 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 two days. Father's Day is in five days.