June 10: ORD

Today is June 10th. It's the 162nd day of the year. 204 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 56. I've calculated the 33-year averages at 77 and 55.

On the hot side, in 2000 (O'Hare's second warmest June 10th) the high was 88 with a low of 72 (tied with the low of 72 in 1959 as O'Hare's warmest lows of the date). Two years later, in 2002, the high was 88 with a low of 71. Three years prior, in 1999, the high was 90 with a low of 67. The record high of 98 was set back in 1911, at a time when the official readings were taken adjacent to Lake Michigan. The record warmest low of 74 occurred back in 1933 at the University of Chicago. 26 of the past 33 highs (79%) were in the: 70s (13) and 80s (13). O'Hare recorded consecutive 70s & 80s highs as follows: seven from 1981 through 1987, nine from 1990 through 1998 and six from 2000 through 2005. One high (3%) was in the hot 90s. Six highs (18%) were in the cool: 50s (1) and 60s (5). O'Hare's hottest June 10th was in 1968 as the high was 92 (O'Hare's hottest of the date) with a low of 70.

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 82 with a low of 45, a 37 degree spread. In 1977 the high was 77 with a cold low of 44, a 33 degree spread. In 1974 the high was a cool 66 degrees. In 1973 the high was a hot 90 degrees. In 1972 the high was 57 with a low of 40, a cool day. In 1968 the high was 92 with a low of 70, a hot day. In 1966 the high was 65 with a low of 44, a cool day. In 1961 the high was 89 with a low of 58, a 31 degree spread. In 1959 the low was a warm 72 degrees.

More recently, the spreads were all large: 37 degrees in 1994 (80/43), 34 degrees in 1987 (78/44), 31 degrees in 1995 (83/52), 30 degrees in 1992 (79/49) and 30 degrees in 1997 (82/52).

On the cool side, in 1980 (O'Hare's second coolest June 10th) the high was 57 (ties the high of 57 in 1972 as O'Hare's coolest high of the date) with the record low of 42. In 1988 the high was 68 with a low of 44. The other cool lows were 43 in 1994 (our most recent 40s low) and 44 in 1987. The other cool high was 63 in 2006. The record coolest high of 54 occurred way back in 1883, at a time when the official readings were taken adjacent to Lake Michigan. 20 of the last 33 lows (61%) were in the 50s. O'Hare recorded six consecutive 50s lows from 2006 through last year, 2011. Five lows (15%) were in the cool 40s. Eight lows (24%) were in the warm: 60s (6) and 70s (2). Our most recent 60s low was 67 in 2005. An interesting observation is that all of the 40s lows (over the last 33 years) occurred between 1980 and 1994. O'Hare's coolest June 10th was in 1972 as the high was 57 (tied with 1980 as O'Hare's coolest high of the date) and low of 40 (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 5:17. Sunset is at 20:29 and twilight ends at 21:04. There's a total of 15 hours, 12 minutes of daylight today and 16 hours, 22 minutes between twilights. We didn't gain or lose daylight from yesterday. Tomorrow twilight begins at 4:42 and sunrise is at 5:16. The moon is waning gibbous, heading towards last quarter tomorrow at 5:41. Illumination was 62% at midnight, will be 57% at noon and 52% at midnight tonight. Moonrise was at 0:16 this morning. Moonset is at 12:11 this afternoon. Moonrise is at 0:43 tomorrow morning. Moonlight time is 11 hours, 55 minutes which is 48 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 four days.