June 20: ORD

Today is June 20th. It's the 172nd day of the year. 194 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 60. I've calculated the 33-year averages at 82 and 60.

On the hot side, in 1988 (O'Hare's hottest June 20th) the high was the record high of 104 with a low of 73, a 31 degree spread. In 1953 the high was also 104 degrees. The high of 104 in 1988 tied July 13, 1995 as the hottest temperature ever in O'Hare's history. In 1995 (June 20th) the high was 95 with a low of 74. 1988 and 1995 were two of our hottest summers. Two years later, in 1997, the high was 89 with a low of 74. Those lows of 74 were O'Hare's warmest of the date. In 2002 the high was 91 with a low of 72, our most recent 90s high and most recent 70s low. The other hot high was 94 in 1991.  The record warmest low of 78 occurred in 1953 at Midway. 25 of the past 33 highs (76%) were in the: 70s (14) and 80s (11). O'Hare recorded consecutive highs in the 70s & 80s as follows: eight from 1980 through 1987 and nine from 2003 through 2011. Seven highs (21%) were in the hot: 90s (6) and 100s (1). One high (3%) was in the cool 50s. There have been no highs in the 60s the past 33 years! O'Hare's most recent 60s high was 65 in 1970. There were five 60s highs from 1960 through 1970.

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 90 with a low of 60, a 30 degree spread. In 1970 the high was a cool 65 degrees. In 1969 the high was a cool 62 with a low of 49, a cool day. In 1968 the low was a cold 48 degrees. In 1963 the high was 63 with a low of 46, a cool day. In 1961 the high was 65 with a low of 47, a cool day. In 1960 the high was a cool 68 degrees.

More recently, the additional spreads were large: 34 degrees in 2005 (86/52), 33 degrees in 1980 (76/43), 33 degrees in 1985 (77/44) and 32 degrees in 1991 (94/62).

On the cool side, in 1992 (O'Hare's coolest June 20th) the high was the record coolest high of 57 with the co-record low of 43. In 2003 the high was 73 with a low of 45. The other cool lows were the co-record low of 43 in 1980, 44 in 1985 and 48 in 2004 (our most recent 40s low). 17 of the last 33 lows (52%) were in the 60s. Twelve lows (36%) were in the cool: 40s (5) and 50s (7). Four lows (12%) were in the warm 70s.

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 is waxing crescent, having reached new yesterday at 10:02. Illumination was 0% at midnight, will be 1% at noon and 3% at midnight tonight. Moonrise was at 6:18 this morning. Moonset is at 21:17 tonight. Moonrise is at 7:18 tomorrow morning. Moonlight time is 14 hours, 59 minutes which is 15 minutes shorter 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. Independence Day is in 14 days. The summer solstice is tonight at 18:09.